Medical Definition of sepia
1 capitalized : a genus (the type of the family Sepiidae) of oval-bodied cephalopods that comprise the cuttlefishes and have a saclike organ containing a dark fluid and an internal shell mostly of calcium carbonate which has been used as an antacid and in tooth and polishing powders
2: the inky secretion of a cuttlefish or a brown pigment from it
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