fall in

verbs

break down, literally or metaphorically

"The wall collapsed"; "The business collapsed"; "The dam broke"; "The roof collapsed"; "The wall gave in"; "The roof finally gave under the weight of the ice"

break, cave in, collapse, fall in, founder, give, give way

to take one's place in a military formation or line

"Troops fall in!"

fall in

become part of; become a member of a group or organization

"He joined the Communist Party as a young man"

fall in, get together, join