Tit for tat

[Donald Trump]

Short for this for that.
To scratch each others backs.
To trade services.

Maryann helps here friend Becky with Beckys homework.
Becky is now obligated to help Maryann with something she needs under the tit for tat rule.

[Justin Bieber]

To show ones tits in exchange for seeing anothers tats

[Tina]

A term made famous in a Jane Russell movie where she stands large- breasted between two cowboys. One cowboy says You stole my horse so I stole your girl. The other cowboy answers Yeah, tit for tat.

[Couch Potatoe]

a very popular way for females into tatooing them selves to pay for said tatoos. this method usualy works considering any tatoo artist, male or female is more then happy to get a little tit in exchange for a little tat.

[Britney]

When a womans tit is seen accidentally by a man, it is only right that the man show his package to her as well.
And if youre lucky, it may lead to something else..

Also works vice versa.

[Justin Bieber]

actions done intentionally to punish other people because they have done something unpleasant to you: