To be angry, agitated, or in a frenzied state. Grandpa was riled up as soon as Uncle Ned mentioned the local election.

To become angry or agitated or enter into a frenzied state. Grandpa got all riled up as soon as Uncle Ned mentioned the local election.

To cause someone or some group to become particularly excited and animated, especially in an angry or irritated manner. A noun or pronoun can be used between "rile" and "up." Seeing that kind of injustice on the news always riles me up to no end. The politician has a knack for riling up his rallies with rhetoric that demeans and vilifies his opponents. The boss's comments really riled Sarah up.