in one's behalf or[on one's behalf] {adv. phr.}, {informal} 1. For someone else; in your place. * /My husband could not be here tonight, but I want to thank you on his behalf./ 2. For the good of another person or group; as a help to someone. * /My teacher went to the factory and spoke in my behalf when I was looking for a job./ Compare: IN BEHALF OF, ON ONE'S ACCOUNT.