Faking is pretending you have an orgasm during lovemaking. Girls fake it because they|:
don’t want to disappoint their lover;
 want to feel sexy;
want intercourse to end;
want the illusion of a simultaneous orgasm, because in their mind that’s the way it’s supposed to be.

Pros and cons of faking

How do you know a girl is faking?
How do I tell my boyfriend I have been faking orgasms?
How can I prevent my girlfriend faking orgasm?

see also: orgasm