/tweek/ , v.t.
1. to pinch and pull with a jerk and twist: to tweak someone's ear; to tweak someone's nose.
2. to pull or pinch the nose of, esp. gently: He tweaked the baby on greeting.
3. to make a minor adjustment to: to tweak a computer program.
n.
4. an act or instance of tweaking; a sharp, twisting pull or jerk.
[ 1595-1605; akin to TWITCH ]