The modern euphemism for "macking" or "hitting on someone." Best used in a situation where a 3rd person party is explicitly and obnoxiously saying "holla holla" in front of the two people.
Jessie Wen and Zack Proman tell each other to "SMIV" and "SMID", respectively. While Jessie claims this to be FALSE, we nevertheless don't believe her. When she asks for Proman's AIM, we say, "HOLLA HOLLA!"