A2
describes people who know each other very well and like each other a lot, or who see and talk to each other a lot
Dictionary examples:
We're so close, we finish each other's sandwiches! (0.0)
We're so close, our phones finish each other's text messages! (0.0)
My closest friend and I have matching 'Best Friends' socks! (0.0)
Mira is one of my closest friends. (9.2)
My brother and I have become much closer over the years. (27.6)
Her relationship isn't good with her father, but she's very close to her mother. (29.3)