in there
when a person is sexually attracted to you and making advances or signals
She was in there!
in there
to have succeeded in reaching first base and above with a person of opposite sex.
You're in there with that bird mate
in there
to have one's penis inside of a female. this can refer to having one's penis inside a female's vagina, mouth, etc.
I had a good time last night. After the party was over, I made sure I was in there, sticking it into all the girls who had followed me back to my apartment.