1. To do something dastardly.
2. To do something daring, courageous, dangerous, or otherwise risky.
3. To masterbate.
"He finally did the deed... she's going to find an interesting surprise in her locker after third period."
"Well, I'm off to do the deed. Wish me luck on my chemistry final."
"What'cha doin'?" "I'm doin' the deed." "Eugh, that's dastardly."