Straight up

[Couch Potatoe]

To be right or for real

[Sarah]

absolutely, totally

[Mark Zuckerberg]

to be honest, to not lie, to not hide things behind others backs. An abbreviation of the term straight up is SU.

[Britney]

without ice (used when describing drinks)

[Sarah]

NO lies, Honesty, Truthfulness, No B.S., The Real Deal, Word up, etc...

[Tanya Shivari]

Pure, absolute, sh*t like that.

[Rihanna]

Means you are being very serious. no joking here.

[Britney]

being honest, telling the truth

[Luis Fok]

To do something honestly, definitely, exactly, or without making a mistake.
It is often said for emphasis

[Monty]

used to show that you are telling the truth: