Lewis & Short

pĕr-ĭnīquus, a, um, adj.

  1. I. Very unfair, very unjust: quare videant, ne sit periniquum et non ferendum, Cic. Imp. Pomp. 22, 63.
  2. II. Very unwilling, very discontented: etsi periniquo patiebar animo, te a me digredi, Cic. Fam. 12, 18, 1.