taxi vs minicab

taxi and minicab both are nouns.

Word	Noun	Adjective	Verb	Adverb
taxi	Yes	No	Yes	No
minicab	Yes	No	No	No

As nouns, minicab is a hyponym of taxi; that is, minicab is a word with a more specific, narrower meaning than taxi:

taxi: a car driven by a person whose job is to take passengers where they want to go in exchange for money
minicab: a minicar used as a taxicab

Other hyponyms of taxi include gypsy cab.

taxi (noun)	minicab (noun)
a car driven by a person whose job is to take passengers where they want to go in exchange for money	a minicar used as a taxicab

taxi (verb)	minicab (verb)
ride in a taxicab
travel slowly