dathkelano

Dath: Literally meaning "Teeth" in the Indian Language Bengali.
Kelano: here, expressed as "To show"

Together, it literally means "To show of your teeth". But the expression is a Bengali slang which expresses the situation where one laughs on someone or something which is not funny to the person or things he/she is laughing on. It's can be expressed as a "Mocking laugh".