To get together is to meet up as a group socially. No agenda beyond seeing each other.
The noun get-together is a small informal party, and suggesting one is deliberately casual, since calling it a party would raise expectations. It takes with. There are two other senses: getting together with somebody can mean starting a relationship, and getting a plan together means organising it. Getting it together is an informal phrase for finally becoming organised.
1phraseget togetherTo meet socially as a group.
“We should get together before Christmas.”
Practised in Phrasal Verbs, A Man Called Ove
First appears in chapter 10 of A Man Called Ove.
Practise this word