deadly (Adjective) — Causing or capable of causing death. ex. "a deadly enemy"
deadly (Adjective) — Of an instrument of certain death. ex. "deadly poisons"
deadly (Adjective) — Extremely poisonous or injurious; producing venom. ex. "deadly snakes"
deadly (Adjective) — (theology) involving loss of divine grace or spiritual death. ex. "the seven deadly sins"
deadly (Adjective) — Exceedingly harmful.
deadly (Adjective) — (of a disease) having a rapid course and violent effect.
deadly (Adjective) — So lacking in interest as to cause mental weariness.
deadly (Adverb) — As if dead.
deadly (Adverb) — (used to intensify) extremely. ex. "deadly dull" ex. "deadly earnest"