Hey Asad Jaat,

A negative thigmotropism is a response away from the touch stimulus. 

An example of negative thigmotropism is the growth of roots underneath the soil. When an elongating root comes in contact with an object, e.g. rock, it grows away from the object.

The drooping of leaflets of Mimosa pudicawhen touched is not considered thigmotropism but a nastic movement. It is because the response of this plant is not influenced by the direction of stimulus, which is a characteristic of thigmotrophic movements.

Hope this will help.