trihydro-Chem.|traɪˈhaɪdrəʊ|[f. tri- 5 + Gr. ὑδρο-, combining form of ὕδωρ water: see hydro-.]A formative denoting that the compound contains the elements of three molecules of water, H2O, united to the substance designated by the rest of the name; e.g.trihydrostrychnine, C21H28N2O5, which differs from strychnine, C21H22N2O2, by 3H2O.1879Jrnl.Chem.Soc. XXXVI. 387 Another basic substance was obtained, trihydrostrychnine.