break off

1.  Stop abruptly, as in The trade talks broke off yesterday. [First half of 1300s]
2.  Separate, sever a connection, as in The baby broke off the tops of all the flowers, or The new sect has broken off from the established church. [First half of 1500s]
3.  End a relationship or friendship, as in Mary broke off her engagement to Rob. [Mid-1600s]

Definition: end activity
Antonyms: begin, start

v

Definition: snap off something
Antonyms: combine, join, mend

The verb has 5 meanings:

Meaning #1: interrupt before its natural or planned end
  Synonyms: cut short, break short

Meaning #2: prevent completion
  Synonyms: break, discontinue, stop

Meaning #3: break off; of a piece from a whole
  Synonyms: chip, chip off, come off, break away

Meaning #4: break a piece from a whole
  Synonyms: break, snap off

Meaning #5: break a small piece off from
  Synonyms: chip, knap, cut off