sap·o·na·ceous \|sapə|nāshəs\adjective Etymology: New Latin saponaceus, from Latin sapon-, sapo soap (of Germanic origin) + -aceus -aceous; akin to Old English sāpe soap — more at soap 1.: resembling soap : having the qualities of soap : soapy 2.: liable to slip away : ingratiating but evasive : elusive • sap·o·na·ceous·nessnoun-es