Ambuscade, a manoeuvre in warfare, whose general nature is indicated by the original Italian imboscata ('concealed in a wood'), but which now applies to any attempt to attack an enemy by lying in wait and coming upon him unexpectedly. The tactics of modern times render ambuscades unusual in civilised warfare. It is something more sudden and unexpected than a 'surprise.'
See Colonel Malleson's Ambushes and Surprises (1883).