From Longman Dictionary of Contemporary Englishsquare up phrasal verb1 OWEto pay money that you owe I’ll pay for the drinks and you can square up later.2 British EnglishFIGHT to get ready to fight someone to The two lads squared up to each other.3 square up to somebody/somethingDEAL WITH to deal with a difficult situation or person in a determined way → square→ See Verb tableFrom Longman Business Dictionarysquare up phrasal verb [intransitive] to pay money that you oweI’ll pay for the drinks and you can square up later. → square→ See Verb table
