Synonyms for Agent (same or very similar meaning)
WordNet sense 1 (any agent or representative of a federal agency or bureau):
federal agent
WordNet sense 2 (a businessman who buys or sells for another in exchange for a commission):
broker, factor
WordNet sense 3 (the semantic role of the animate entity that instigates or causes the happening denoted by the verb in the clause):
agentive role
From the ODE community, based on WordNet
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