the act of tickling
"The cat spent all afternoon chasing its tail, much to our amusement at the sight of it engaging in such silly behavior."
A sensation that tickles.
"The soft breeze against her cheek created a gentle, pleasant tickling sensation."
present participle of tickle
"The cat spent all afternoon chasing her own tail, creating a sensation of tickling fur that made her laugh uncontrollably."
In plain English: To tickle is to lightly touch someone's skin with your fingers, hand, or something else so that they laugh uncontrollably.
"The gentle breeze was tickling his face with soft leaves."
exciting by touching lightly so as to cause laughter or twitching movements
"The feather tickled his foot, making him laugh uncontrollably while his toes curled in response."
That tickles
"The gentle breeze against her cheek felt like that tickles."