glycolaldehyde
noun
gly·col·al·de·hyde
| \ ˌglī-(ˌ)kȯl-ˈal-də-ˌhīd, -(ˌ)kōl-
\
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Medical Definition of glycolaldehyde
: a compound that exists in solution as the diose C2H4O2 but that exists in the anhydrous state only as the crystalline dimer C4H8O4