Definition of substitution. 1  1a : the act, process, or result of substituting one thing for anotherb : replacement of one mathematical entity by another of equal value. 2  2 : one that is substituted for another.
Homogenized milk is any sort of milk that has been mechanically treated to ensure that it has a smooth, even consistency. The homogenization process typically involves high temperatures, agitation, and filtration, all aimed at breaking down milk's naturally occurring fat molecules.
noun. 1  The part of milk that coagulates when the milk sours or is treated with enzymes. 2  A lump of curd: cheese curds. 3  A coagulated liquid that resembles milk curd.