Noun | 1. | ![]() conditioner - a substance used in washing (clothing or hair) to make things softer plasticiser, plasticizer - a substance added to plastics or other materials to make them more pliable chemical, chemical substance - material produced by or used in a reaction involving changes in atoms or molecules water softener - a substance (such as sodium chloride) that lessens the hardness of water by replacing calcium and magnesium ions with sodium ions and so gives the water more efficient sudsing power |