Available Definitions:
1) n. - The stoke of a bell tolled at a funeral or at the death of a person; a death signal; a passing bell; hence, figuratively, a warning of, or a sound indicating, the passing away of anything.
2) n. - To sound as a knell; especially, to toll at a death or funeral; hence, to sound as a warning or evil omen.
3) v. t. - To summon, as by a knell.