Answer :

Contextual symbol is a word or object that stands for something else just in the story or situation.

For example . Do you know the sign with a skull and 2 bones crossed behind him) I think you do. . The skull and crossbones stand for poison. So, if you see the symbol( you can try typing it on google) on a box or bucket, please don’t eat what is inside of the container.
It's that simple... Hope it helped
emilyadalex

A contextual symbol is a symbol whose meaning is not widely recognized by a society or culture, but that can only be recognized within the context or framework of a specific story because these are unique symbols that authors created  to serve a certain purpose in the story.

An example of contextual symbol is the White Whale in the Moby-Di.ck novel by Herman Merville, that is said to represent God, the divine or nature as it is powerful and can not be tamed or beaten. This character works as a contextual symbol because it can only be recognized as such  by the readers of the novel.