A blunder, an error.
A fly ball that is weakly hit just over the infielders.
A gaff-rigged fore-and-aft sail set from and aft of the aftmost mast of a square-rigged ship; a spanker.
The Vietnam-era M79 grenade launcher (due to its distinctive report).
A filmed or videotaped outtake that has recorded an amusing accident and/or mistake.
A careless mistake made in thinking.