v.
  - lightly touch in a way that causes itching or twitching and often laughter. 
▸catch (a trout) by lightly rubbing it so that it moves backwards into the hand.
 - be appealing or amusing to.
 
n.
 an act of tickling or sensation of being tickled.
 
  Phrase
  
    - be tickled pink 
(or to death)
 informal be extremely amused or pleased.  - tickle the ivories
 informal play the piano. 
   
  Derivative
  
  Etymology
  ME: perh. a frequentative of tick1, or an alt. of Scots and dial. kittle ‘to tickle’ (cf. kittle).