Wikipedia
A target of opportunity is a target "visible to a surface or air sensor or observer, which is within range of available weapons and against which fire has not been scheduled or requested." A target of opportunity comes in two forms; "unplanned and unanticipated". __TOC__
Usage examples of "target of opportunity".
Actually I believe it was your mother the man was aiming at, as a target of opportunity.
Ritter turned to take out his anger on the nearest target of opportunity.
Blocked twice, visibly suffering from his profound misstep, Piotr looked around for a target of opportunity upon which to vent his frustration.
We have a target of opportunity and are sending a stealth fighter to go after it.
I've been kinda hoping that the hits so far might generate a target of opportunity, but nobody's prairie-dogging yet.
The air team saw a target of opportunity and took it, but they were detected before they could attack.
Your immediate objectives will be to coordinate additional intelligence assets with FIST intelligence, prepare a ready force to rescue any recon team that gets into trouble, and prepare a ready force to strike at any target of opportunity disclosed by F2.
They must have had business with Morley and I was just a target of opportunity.
One, up in a tree, took the first target of opportunity and pounced down on a trooper, dismounting him.
Whether this whole business was instigated by the enemy from the start or merely co-opted as a target of opportunity is beside the point.