tweak

Concise Oxford English Dictionary © 2008 Oxford University Press:
tweak/twiːk/

▶verb

• 1 twist or pull with a small sharp movement.

• 2 informal improve by making fine adjustments.

▶noun

• 1 an act of tweaking.

• 2 informal a fine adjustment.

– derivatives
tweaker noun.

– origin C17: prob. an alt. of dial. twick ‘pull sharply’; rel. to twitch.