lark
n.a small bird known for its beautiful singing, or a fun activity you do just for a joke. You might do something 'for a lark' if you want to be a bit silly.
n.refers to any of several small songbirds, particularly the Alauda arvensis, or a lighthearted, mischievous adventure. Often appears in the idiomatic phrase 'on a lark' or 'for a lark' to indicate spontaneous fun.
“We went for a swim at midnight just for a lark.”
“The morning air was filled with the sweet, rising song of a lark in the meadow.”
“What began as a harmless lark among university students quickly escalated into a local scandal that required the dean's personal intervention.”
When referring to a prank or fun activity, it is frequently used with the prepositions 'on' or 'for'.
“There were a few candid ones like that; people just crashed out, maybe having a rough time.” Subway sect … Punks larking about on the Northern line, circa 1990.”
“I am tired.” Swishing about are uncertain memories of a childhood “shrouded” in nightmares: there was an orchard with an abundance of flora and fauna, and larks and swallows and “swifts to scream”.”