What is the meaning of Tweak?

To pinch and pull with a sudden jerk and twist; to twitch.

To adjust slightly; to fine-tune.

To tease, to annoy; to get under the skin of (someone, typically so as to irritate them, or by extension to enamor, frighten, etc).

To abuse methamphetamines, especially crystal meth.

To exhibit extreme nervousness, evasiveness when confronted by authorities, compulsiveness, erratic motion, excitability, etc, due to or mimicking the symptoms of methamphetamine abuse.

To be extremely confused; to have no clue what is going on.

A sharp pinch or jerk; a twist or twitch.

A slight adjustment or modification.

Trouble; distress; tweag.

A prostitute.

An additional input to a block cipher, used in conjunction with the key to select the permutation computed by the cipher.

Source: wiktionary.org