1. Break down, literally or metaphorically
   - collapse, cave in, give, give way, break, founder 
2. To take one's place in a military formation or line
   "Troops fall in!" 
3. Become part of; become a member of a group or organization
   - join, get together

Derived forms: fell in, falls in, falling in, fallen in

See also: fall

Type of: change

• get behind
• get by
• get cracking
• get down
• get down to brass tacks
• get dressed
• get even
• get going
• get hitched
• get hitched with
• get hold
• get hold of
• get in
• get in touch
• get into
• get it
• get it on
• get knotted
• get laid
• get lost
• get married
• get moving
• get off
• get off the ground
• get on