monosymmetric
/ˌmɒnə(ʊ)sɪˈmɛtrɪk/adjective
Chiefly Botany. Divisible into exactly similar halves in one plane only; (of a flower) zygomorphic. Also ( Engineering ): having, or designating a cross-section with, a single plane of symmetry.
Origin
Late 19th century (in an earlier sense). From mono- + symmetric.