Tickle

1. a. Wavering, or liable to waver and fall at the slightest touch; unstable; easily overthrown.
2. v. t. To touch lightly, so as to produce a peculiar thrilling sensation, which commonly causes laughter, and a kind of spasm which become dengerous if too long protracted.
3. v. t. To please; to gratify; to make joyous.
4. v. i. To feel titillation.
5. v. i. To excite the sensation of titillation.
6. a. Ticklish; easily tickled.
7. a. Liable to change; uncertain; inconstant.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.