A friend of the female gender. The English language had previously made it too easy for women to make their boyfriend or would-be suitor jealous by telling him she's "out with a friend". Back then, for the next several hours after receiving that "with a friend" text from her, his mind would go from convincing himself that the friend is a girl from her pilates class, to thinking that this "friend" is a 6'3" surgeon taking her out on his 75 ft yacht. And back and forth between those thoughts. In reality, it was her childhood friend, Sarah, that she was with, but she knew what she was doing when she said to him "a friend" just to drive him to insanity in a seemingly innocent and unintentional way. Because, of course, if he had asked the sex of this friend, he would appear to be a jealous psycho. And he is still trying to play it cool.
Boy: babe where are you?
Girl: I'm home waiting for a friend to come by to get something from me.
Boy: (imagining friend means some dude and something means sex). "Um .. uh.. ok"
Girl: not like that silly, it's a frienda.
Boy: oh! you should've said so to begin with! If only women started clarifying that they're with a frienda, it would save men hours of looking at your Facebook page for any check-ins, excessive "likes" from random dudes, or other such unusual activity.
Similar to the Spanish word "amiga".
See also: friendo
Bill: No, I am going with my frienda, Haley.