alarm vs alarm clock

alarm and alarm clock both are nouns.

Word	Noun	Adjective	Verb	Adverb
alarm	Yes	No	Yes	No
alarm clock	Yes	No	No	No

As nouns, alarm and alarm clock are synonyms defined as:

alarm (noun)	alarm clock (noun)
a device that signals the occurrence of some undesirable event	a clock that wakes a sleeper at some preset time
a clock that wakes a sleeper at some preset time
an automatic signal (usually a sound) warning of danger
fear resulting from the awareness of danger

alarm (verb)	alarm clock (verb)
warn or arouse to a sense of danger or call to a state of preparedness
fill with apprehension or alarm; cause to be unpleasantly surprised