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Webster 1913 Edition

Adj.

[L.

bis

twice +

membrum

member.]

(Gram.)

Having two members;

as, a

bimembral

sentence

J. W. Gibbs.

bimembral ‎(not comparable)

(grammar) Having two members.
- 1858, Josiah Willard Gibbs, A Latin Analyst on Modern Philological Principles
  This will be more easily apprehended, if we consider that all combination is bimembral; i. e. consists of two members, one of which is subordinated to the other by the intonation, and thus becomes compacted with it […]