e·ryth·ro·blast 
(ĭ-rĭthrə-blăst′)
(ĭ-rĭthrə-blăst′)n.
Any of the nucleated cells normally found only in bone marrow that are precursors of erythrocytes.
[German Erythroblast : erythro-, erythro- (from Greek eruthros, red; see ERYTHRO-) + -blast, -blast (from Greek blastos, bud, germ; see -BLAST).]
e·ryth′ro·blastic adj.