Trying Out Copilot Custom Dictionary

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💻 Trying Out Copilot Custom Dictionary

topics: [copilot, Microsoft 365, Microsoft 365 Copilot]

When using AI for meeting minutes, there are many cases where company or product names are not recognized correctly, or the AI cannot grasp the context due to internal jargon, resulting in low-accuracy transcripts. For someone like me who doesn't always enunciate clearly, it's even more common for transcriptions to go wrong. To address these issues, a new feature for Microsoft 365 Copilot's Teams meeting transcripts, "Copilot Custom Dictionary," began rolling out between June and July 2025, so I decided to try it out right away.

This blog post is based on information as of July 5, 2025.

What is Copilot Custom Dictionary?

This is a feature for Microsoft 365 Copilot's Teams meeting transcripts (Intelligent Recap) that enables the accurate recognition of organization-specific terminology. By registering your company's product names, project names, and technical terms, you can improve the accuracy of meeting transcripts.

Applicable Meetings

  • Scheduled Teams meetings
  • Town halls
  • Webinars

Alert: Currently, 1-on-1 calls and ad-hoc calls are not supported.

Setup Method

Prerequisites

  1. Admin Rights: Global administrator or AI administrator
  2. License: Microsoft 365 Copilot license
  3. Preview Participation: Enrollment in the Teams Public Preview program

Setup Steps

1. Access the Admin Center

Sign in to the M365 admin center, and from the left menu, select "Copilot" → "Settings" → "Other settings".

Screenshot 2025-07-05 065819

2. Download the Template

Select "Copilot Custom Dictionary" and click "Upload". When the template options appear, download the "CSV template with header only" file.

Screenshot 2025-07-05 072657

3. Edit the CSV File

Open the template and add your terms in the format shown in the example below. I'm still experimenting to find the best way to register terms and will update this post when I find an effective pattern. The example includes various Japanese terms such as departmental abbreviations (e.g., IS, 情シス), slang (e.g., ポンチ絵, なるはや), and fictional project/product names to show the range of possibilities.

Term (required),Sounds like,Long form of the term (for acronyms),Definition and context
IS,aiesu,情報システム部,社内の情報システムを管理する部署
情シス,zyousisu,情報システム部,社内の情報システムを管理する部署
品証,hinsyou,品質保証部,品質保証部の略称
DX,di-ekkusu,デジタルトランスフォーメーション推進部,社内のデジタルトランスフォーメーションを推進する部署
経企,keiki,経営企画部,経営企画部の略称
コパ活,kopakatu,Copilot活用,Copilot活用を広めていくための取り組み
GSP,gi-esu-pi-,Global Security Policy,グループグローバルで定められたセキュリティ規定
コパソウ,kabushikigaisha copilot souken,株式会社copilot創研,主要取引先企業名
ポンチ絵,ponchie,,会議などで使用される簡単な概念図やスケッチ
なるはや,naruhaya,なるべく早く,「なるべく早く」の略語。緊急性を伝える際に使用
よしなに,yoshinani,,「いい感じに」「適切に」という意味。相手に裁量を任せる際に使用
あいみつ,aimitsu,相見積もり,複数の業者から見積もりを取り、比較検討すること
たたき台,tatakidai,,議論のベースとなる初版の草案や提案
サマる,samaru,要約する,要約する（summarize）の和製英語
魁プロジェクト,sakigake purojekuto,,新規事業の社内コードネーム
蒼天ソリューション,souten soryuushon,,架空の主力製品・サービス名
Zenithシステム,zenisu shisutemu,,社内で開発された基幹業務システム名
KAIZEN会議,getsuji teirei kaizen kaigi,KAIZEN会議,毎月行われる業務改善のための定例会議

Alert: According to Microsoft Learn[1], it seems that "Sounds like" and "Long form of the term (for acronyms)" are not currently used but are planned for future use. Also, for the Japanese dictionary, I am still investigating whether it's better to write "Sounds like" in romaji or kana (e.g., for GSP, whether to write "gi-esu-pi-" or "ジーエスピー"). I will update this post as soon as I find out.

4. Upload

Save the CSV file in "CSV UTF-8" format and upload it in the admin center. When doing so, select the target language (e.g., Japanese).

Reflection Time

After the setup is complete, it will take up to 24 hours to be reflected across the entire tenant.

Trying It Out

To be honest, it's difficult to test the performance of voice-related tasks on my own. However, my impression is that after registering a word like "Kopakatsu" (a custom term for 'Copilot utilization'), Copilot now seems to capture it correctly, whereas before it would often be misrecognized as something else due to my poor enunciation. It also seems to have gotten better with organizational abbreviations (e.g., "Keiki" for Corporate Planning Department, "Hinshou" for Quality Assurance Department), but in my test case, the before-and-after difference was subtle, so I didn't get a strong sense of a dramatic improvement.

I believe this feature will be more impactful for large companies with a lot of internal jargon, so I encourage you to try it out for yourself.

Limitations

Technical Limitations

  • Max 500 words: Limited to 500 words per dictionary file (per language).
  • Admin-only updates: General users cannot edit; admin rights are required.
  • One file per language: Multiple dictionaries for the same language are not allowed.
  • Complete overwrite: Updating completely replaces the existing dictionary.
  • No group or user targeting: Currently, you cannot specify the scope to groups or users.

Unsupported Meetings

  • 1-on-1 calls
  • Unscheduled group calls
  • Meetings started by users without a Copilot license

Not to be Confused with Copilot Tuning

This feature is different from "Copilot Tuning"[2], which was announced at Microsoft Build in May 2025. Copilot Tuning is currently only available in an early preview for customers with 5000 or more Microsoft 365 Copilot licenses.

Summary

To maximize your investment in Microsoft 365 Copilot, I hope you will consider implementing the custom dictionary. Accurate transcription is the foundation for more advanced AI features.

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