You use suspect when you are stating something that you believe is probably true, in order to make it sound less strong or direct.

If you suspect that something dishonest or unpleasant has been done, you believe that it has probably been done. If you suspect someone of doing an action of this kind, you believe that they probably did it.

A suspect is a person who the police or authorities think may be guilty of a crime.

Suspect things or people are ones that you think may be dangerous or may be less good or genuine than they appear.