Lying in ambush, concealed so as to make a surprise attack. Also: caught in an ambush, waylaid. Frequently figurative.

That waylays (in various senses).

That ambuscades or lies in ambush; given to or characterized by ambushing; = ambushing, adj. Also figurative.

Of something or someone unwelcome, harmful, etc.: widespread, prevalent, endemic; flourishing or spreading unchecked; spec. (of a disease) raging.

Placed or concealed in ambush; = ambushed, adj. 2.