1.
Enter a place, as in We managed to get in just before the doors closed. [First half of 1500s]
2.
Arrive, as in We got in late last night. [Early 1600s]
3.
Be elected to office or become accepted, as in a club. For example, Marge asked the club if she could get in. The variant
get into takes an object, as in Things changed after he got into office. [Late 1500s]
4.
Succeed in including, delivering, or finishing something, as in Can you get in that last paragraph? or I hope you'll get it in on time. Also see get in with.