Student or Learner
Is this the symbol of "opposite" ? Example : "black # white" ?
Like Raymott, I've never seen a symbol for "opposite". If there were one, we wouldn't simply put it between (as in your example) two colours because "black opposite white" is an unlikely construction.
Black is the opposite of white - but then the symbol would have to mean "is the opposite of".
Remember that we have to be careful about how we use the word ‘opposite’ in language:
"Opposites. A word might have two opposites: the opposite of short might be long or tall, depending on if we are referring to a person's hair or a person's height. The opposite of a bad case of poison ivy is not a good one, but a mild one, and the opposite of rock-hard would not be rock-soft, but might be expressed as baby-soft.
Also, it is hard to say what an opposite is. Is enemy the opposite of friend? Friend might be contrasted with enemy in a proverb like, "A thousand friends are not enough, one enemy is too many." But in naturally occurring language friend is more often connected with words like the following: "family, friends and acquaintances," "friends, neighbors, co-workers," "friends and acquaintances," etc."
Stockdale - Definition Plus Collocation in Vocabulary Teaching and Learning (TESL/TEFL)