The Collaborative International Dictionary
Subsesqui-
Subsesqui- \Sub*ses"qui-\ [Pref. sub- + sesqui
--.] (Chem.)
A prefix (also used adjectively) denoting the combination of
constituents (especially electro-negative and
electro-positive bodies) in the proportion of two to three;
as, a subsesqui acetate, i. e., a salt having two equivalents
of acetic acid to three of the base.