Ripping a piece 

to smoke weed

Ted and I plan on ripping a piece later

Ripping a piece by TwistedAngel October 26, 2008

Rippin' off a piece 

Having illicit sexual relations with someone who is involved in a relationship. Can be used in non-adulterous situations as well.

q: "How come you didn't meet us at the bar last night?"
a: "I was rippin' off a piece of Elaine's fine ass"

or

"Rip me off a piece of that bread"

etc

Rippin' off a piece by derp_derp March 19, 2011