What is Thwack?

A derogatory word, implying someone intentionally masturbating someone else. The word derives from the sound of a penis being slapped.

"Thawck!" - stated by Mr Ben upon seeing his sister go to her room with her boyfriend.

Thwack - meme gif

A firm thumb that a hard penis gives to a female (or male... depending on your taste), in any number of places.

Puedes THWACK tu SCHLONG en mi cara, por favor?
Translation: Can you THWACK your SCHLONG in my face, please?

The sound made by the scrotum striking the belly of a women whilst making love doggy-style

The thwack sound echoed through the room as I reached satiation.

to thwackit is to jackoff, spank the monkey, flonk the dolphin, rope the poney, wrestle with the snake, choke the chicken etc. etc.

jimmy thwacked it all night until his shlong turned chrimsen.

To firmly slap ones penis across another persons face i.e. to be either very manly or very homosexual.

"Dude! That little limp wristed faggot just thwacked me!"

One jock buddy says to another...
"WHOA! Billy's asleep, someone thwack him!"

Nikki thwacked her friend on the arm.
*thwacks you

to be speed up as much as possible off of speed/meth

lets get all thwacked out, go to the titty bar and rub tuna on ourselfs then go home to our women...

to hit hard and percise. Usualy producing a THWACK sound.

With a "THWACK" the bamboo rod hit table.

To receive a hand job or blow job, and to not finish.

"Dude, she was thwacking me for an hour yesterday."
"How did you not finish bro?

Jack: i have reverse card try and beat me bob
Bob: (thinking emoji) Thwack