n 1  cap  :  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 .
 
 
 
Similar sounding terms:  hys·sop  sap  sa·po  soap 
 
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