What is th antonym for caption?

There isn't a single perfect antonym for "caption" because it depends on the context. Here are some possibilities:

If "caption" refers to the text accompanying a picture:

* No text

* No explanation

* Unlabeled

* Blank

If "caption" refers to the act of writing a caption:

* Omit

* Ignore

* Neglect

* Leave blank

If "caption" refers to a title or heading:

* Unentitled

* Unnamed

* Untitled

The best antonym depends on the specific meaning you are trying to convey.