sky

noun
1. the vault of heaven
2. the firmament

lark

noun
1. species of small bird, including the skylark
2. frolic, spree; an amusing incident

skylark

noun
1. Alauda arvensis, a small species of bird—plain in colouring, and not at all like its verbly cousin. The male has broad wings and two or three minutes of song in him; females prefer the male that can sing and hover the longest.

intransitive verb
1. (of sailing) to run up and down the rigging of a ship in sport
2. to gambol; to frolic; to indulge in horseplay; to indulge in lark
3. to play tricks or practical jokes

“Skylarking presents a hazard in the workplace.”
—Australian Occupational Health and Safety Legislation, 1998