Meaning of epimer

ep•i•mer

Pronunciation: (ep'u-mur), [key]
— n. Chem.
  1. either of a pair of isomeric aldose compounds, esp. of certain sugars, that differ from each other in the positions of the H and OH at the second atom from the end of the carbon chain, as d-glucose and d-mannose.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.