Speak for Definition 1 of 3Pro Tip 1/3Group Representation Used when one person expresses the thoughts or decisions of a group. Our class president will speak for all of us during the assembly. Pro Tip 2/3Consent Required Be sure that you have permission to speak on another person's behalf. I'll speak for my colleague, as she asked me to. Pro Tip 3/3Authority Speaker Often, a person needs recognized authority to speak for others. As their lawyer, I am authorized to speak for my clients.