send in Go to send into
1. To order or direct someone to enter some place. A noun or pronoun can be used between "send" and "in." Please tell the receptionist to send in the next applicant. Mom sent me in to the living room to apologize to Sally for taking her toy.
2. To order or cause someone to enter or become involved in some situation. A noun or pronoun can be used between "send" and "in." Don't worry, I'm sending in our top legal adviser to handle the details. We've sent police in to keep the peace during the protest.
3. To submit or dispatch something, typically a document or payment. A noun or pronoun can be used between "send" and "in." I've sent my application in, so hopefully I'll hear back soon. The employees have sent in a letter of complaint to upper management about their working conditions. Did you send in the check for our utility bill yet?
See also: send
send someone in Go to send someone into something