noun
compasses; dividers
Refers to a drawing instrument for circles or measuring distances. The term is somewhat colloquial or informal; the standard word is コンパス.
ぶん回しで円を描く。
Draw a circle with compasses.
noun
revolving stage
Used in theater contexts, synonymous with 回り舞台. Likely a colloquial or jargon term.
See also: 回り舞台 (まわりぶたい)
ぶん回しが回ると場面が変わる。
When the revolving stage turns, the scene changes.
Standard term for revolving stage; ぶん回し is a less common synonym.
Compound of ぶん (emphatic prefix) and 回し (noun form of 回す, 'to turn'). The exact derivation is uncertain; it may have arisen as a colloquial term for tools or mechanisms that rotate.