AMBUSCADE n. 2 definitions
A lying in a wood, concealed, for the purpose of attacking an enemy by surprise. Hence: A lying in wait, and concealed in any situation, for a like purpose; a snare laid for an enemy; an ambush.
AN n.
ies one, or any, but somewhat less emphatically. In such expressions as "twice an hour," "once an age," a shilling an ounce (see 2d A, 2), it has a distributive force, and is equivalent to each, every.