Webster's Revised Unabridged Dictionary · 1913

Tickle

Tickle , transitive verb

[Perhaps freq. of tick to beat; pat; but compare also Anglo-Saxon citelian to tickle, Dutch kittelen, German kitzlen, Old High German chizzilōn, chuzzilōn, Icelandic kitla. Compare Kittle, transitive verb]

1.
To touch lightly, so as to produce a peculiar thrilling sensation, which commonly causes laughter, and a kind of spasm which become dangerous if too long protracted.
If you tickle us, do we not laugh? — Shakespeare
2.
To please; to gratify; to make joyous.
Pleased with a rattle, tickled with a straw. — Pope
Such a nature Tickled with good success, disdains the shadow Which he treads on at noon. — Shakespeare

Tickle , intransitive verb

1.
To feel titillation.
He with secret joy therefore Did tickle inwardly in every vein. — Spenser
2.
To excite the sensation of titillation. — Shakespeare

Tickle , adjective

1.
Ticklish; easily tickled. [Obsolete]
2.
Liable to change; uncertain; inconstant. [Obsolete]
The world is now full tickle, sikerly. — Chaucer
So tickle is the state of earthy things. — Spenser
3.
Wavering, or liable to waver and fall at the slightest touch; unstable; easily overthrown. [Obsolete]
Thy head stands so tickle on thy shoulders, that a milkmaid, if she be in love, may sigh it off. — Shakespeare