usually meaning suspect, acting in a nervous, acting different, out of place.
in this example ant cheated on his girl with her friend.
carl: heyyyyyy baby, u look so beautiful.
Ashley:thanks, u never said that throughout the whole course of our relationship wtf is up.
carl:: nothing i just love you.
*phone rings* (its ashleys homegirl)
homegirl: hey sexy!
Ashley: hold the fuck on cuz yall niggas are acting mad fuckin sus, and why the fuck it smell like sex in this bitch!