monochasyn.
Origin: A variant or alteration of another lexical item. Etymon: monochasium n.
Etymology: Alteration (with suffix substitution: see -y suffix4) of monochasium n.
Botany.
rare. Apparently only attested in dictionaries or glossaries.
1900 B. D. Jackson Monochasy, a uniparous cyme, either pure, or resulting from the reduction of cymes.
This is a new entry (OED Third Edition, December 2002; most recently modified version published online June 2021).