Merriam-Webster's Collegiate® Dictionary, 11th Edition
TICKLE
I. verb (tickled; tickling)
Etymology: Middle English tikelen; akin to Old English tinclian to tickle
Date: 14th century
transitive verb
1. to excite or stir up agreeably ; please , to provoke to laughter or merriment ; amuse , to touch (as a body part) lightly so as to excite the surface nerves and cause uneasiness, laughter, or spasmodic movements, to touch or stir gently , intransitive verb to have a tingling or prickling sensation , to excite the surface nerves to prickle,
II. noun
Date: 1801
the act of tickling, a tickling sensation, something that tickles