• fatal, causing death; (slang) cool; extraordinary; fantastic (as in: "a deadly outfit")
• in a deathly manner; extremely, completely
• if something is deadly, it is likely or able to kill.
• you use deadly to emphasize an unpleasant or serious quality.
• you can also use deadly to say that something is extremely effective, especially in the context of hurting someone.
• dangerous mixture (usually an alcoholic drink or a combination of drugs)
• lethal mixture, dangerous union
• very boring, extremely tedious
• belladonna, poisonous plant with dark purple berries
• lethal poison, substance which is very likely to cause death
• any of the seven deadly sins (pride, covetousness, lust, anger, gluttony, envy and sloth)
• dead time, time in which nothing productive is happening
• lethal virus, microscopic infective agent which causes a deadly disease; life threatening disease caused by such a virus
• lethal weapon, tool that destroys