en·ven·om 
(ĕn-vĕnəm)
(ĕn-vĕnəm)tr.v. en·ven·omed, en·ven·om·ing, en·ven·oms
1. To make poisonous or noxious.
2. To embitter.
[Middle English envenimen, to poison, from Old French envenimer : en-, cover with; see EN-1 + venim, venom; see VENOM.]