Compulsive bird watching by people (twitchers) who travel long distances to see rare species(noun)
Present participle of twitch.(verb)
That twitches.(adjective)
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Use "twitching" in a sentence
"We can’t see them, except for a bit of net curtain twitching from the caravans, and the odd small cluster of garishly dressed ginger-headed teenagers who walk around us in circles, then stand out of earshot to make obvious mobile phone calls."
"The nights he slept away in twitching unconsciousness."
"I was not sniffling, though my face might well have been drawn and twitching from the pain."