a person male or female who frequently engages in sexual activity outside of a committed relationship and has no intention of or desire for emotional involvement or a relationship with his or her sexual partners.
Sluts are often, though not necessarily, characterized by their indiscriminate choice of sexual partners.
"On Sunday mornings as the people make their walk of shame back to their respective homes, you can always pick out the sluts by the fact that they have no idea what part of town they spent the night in." (describes and indiscriminate slut)
"Reuben says he's not a slut he because he only sleeps with his friends, but you see, he's slept with ALL of his friends." (describes a disciminating slut)