What does stifle mean?

to hinder. The man stifled his cough at the church service.

The girl's stifled their giggles as they saw a student pass by with toilet paper stuck to their shoe.

Can all so be used to mean oppressive.

The heat was stifling in the car because the AC was broken.

The rigors of the course requirements were stifling.

He felt stifled by her constant attentions.