branch off phrasal verb (see also branch)

1. if a road, passage, railway etc branches off from another road etc, it separates from it and goes in a different direction Synonym : fork off
branch off from
a passage branching off from the main tunnel

2. British English to leave a main road Synonym : fork off
branch off from/into
We branched off from the main road and turned down a country lane.

3. to start talking about something different from what you were talking about before
branch off into
Then the conversation branched off into a discussion about movies.

[TahlilGaran] Dictionary of Contemporary English ▲

branch off
v. To go from something big or important to something smaller or less important; turn aside.
At the bridge a little road branches off from the highway and follows the river.
Martin was trying to study his lesson, but his mind kept branching off onto what girl he should ask to go with him to the dance.

[TahlilGaran] English Idioms Dictionary ▲