antipsychotic vs major tranquillizer

antipsychotic and major tranquillizer both are nouns.

Word	Noun	Adjective	Verb	Adverb
antipsychotic	Yes	No	No	No
major tranquillizer	Yes	No	No	No

As nouns, antipsychotic and major tranquillizer are synonyms defined as:

antipsychotic and major tranquillizer: tranquilizer used to treat psychotic conditions when a calming effect is desired

antipsychotic (noun)	major tranquillizer (noun)
tranquilizer used to treat psychotic conditions when a calming effect is desired	tranquilizer used to treat psychotic conditions when a calming effect is desired