adj.1. denoting a stimulus dimension in which a change of magnitude can cause a qualitative change in the psychological experience produced. For example, a faint smell may be quite pleasing, whereas an increase in intensity may cause revulsion. Compare prothetic. 2. relating to a change in place or condition, particularly the transposition of two phonemes in a word or the exchange of elements between chemical compounds to create different kinds of compounds. —metathesisn.