Dictionary
ad•stra•tum
Pronunciation: (ad'strā"tum, -strat"um), [key]—
n.,
—pl. -stra•taPronunciation: (-strā"tu, -strat"u). [key]
Historical Ling.
a substratum or superstratum.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.