D defs.my
Entry 1 sense Webster, 1913

Phosphonium

· Phos·pho·ni·um · IPA
01 n. The hypothetical radical PH4, analogous to ammonium, and regarded as the nucleus of certain derivatives of phosphine.
  1. 1.
    The hypothetical radical PH4, analogous to ammonium, and regarded as the nucleus of certain derivatives of phosphine.(Chem.)