Definition of "thumbnail" in English

noun

1. The fingernail on the thumb.

2. A rough sketch (e.g., the size of one's thumbnail).

3. (chiefly computing) A small picture, used as a compact representation of a larger image.

4. (social media) A picture displayed by posts and videos pre-clicked conveying the matters discussed/shown in that post.

verb

1. (transitive) To describe concisely.

2. (transitive, computing) To create a smaller representation of (a larger image).