v. To adopt or accept as a member, subordinate associate, or branch: The HMO affiliated the clinics last year. v. To associate (oneself) as a subordinate, subsidiary, employee, or member: affiliated herself with a new law firm. v. To assign the origin of.verb-intransitive. To become closely connected or associated: The two unions voted to affiliate. n. A person, organization, or establishment associated with another as a subordinate, subsidiary, or member: network affiliates.