LLets say someone has physical deformity and someone making gestures micking the deformity is that harassment?

[Hassaniscool]

[Chazmatazz269]

What it is depends on how it’s received. If the person being mocked is not receptive, or otherwise unable or unwilling to return the gesture, it’s harassment or bullying.
If it’s a couple of people ribbing each other good naturedly, it’s witty banter between friends.
From the outside looking in, it can be difficult to tell the difference at first glance. Further observation and greater understanding of people will help to avoid misunderstandings. Even a cursory knowledge of body language and voice inflections can help an observer get nearer to the truth of the interaction.