special-interest group vs pressure group

special-interest group and pressure group both are nouns.

Word	Noun	Adjective	Verb	Adverb
special-interest group	Yes	No	No	No
pressure group	Yes	No	No	No

As nouns, special-interest group and pressure group are synonyms defined as:

special-interest group and pressure group: an interest group that tries to influence legislators or bureaucrats to act in their favor, typically through lobbying

Other synonyms of special-interest group include advocacy group, lobby, lobby group, special interest, special interest group, third house.

special-interest group (noun)	pressure group (noun)
an interest group that tries to influence legislators or bureaucrats to act in their favor, typically through lobbying	an interest group that tries to influence legislators or bureaucrats to act in their favor, typically through lobbying