Real Dictionary

tickle
verb: If something tickles you or tickles, it causes an irritating feeling by lightly touching a part of your body.
verb: When you tickle someone, you move your fingers lightly over a sensitive part of their body, often in order to make them laugh.

tickle in American English
to have an itching, scratching, or tingling sensation
to please, gratify, delight, etc.
intransitive verb: to be affected with a tingling or itching sensation, as from light touches or strokes
transitive verb: to touch or stroke lightly with the fingers, a feather, etc., so as to excite a tingling or itching sensation in; titillate

tickle in British English
verb: to touch, stroke, or poke (a person, part of the body, etc) so as to produce pleasure, laughter, or a twitching sensation