A fart in which is the signal of trust between a couple. Usually happens when the male farts. The reaction of the female after the fart determines if she trusts you or not.
"I was watching t.v with my girlfriend and decided to give her a trust fart to see what she would do and...
(a) ...she just chuckled, now I know she's the one for me!"
(b)...she said 'oh my god...oh my god' and left....that bitch!"