Boyd’s Bible Dictionary:
(servant). A person chosen by one government to represent it at the seat of another. Earliest mention (Num. 20:14; Josh. 9:4; Judg. 11:17-19). Injury to them an insult to their king (2 Sam. 10:3-6). The term includes both messenger and message (Luke 14:32). Ministers called ambassadors of Christ (2 Cor. 5:20).
Concise Bible Dictionary:
Simply the persons sent as ambassadors, with attendants, and usually with presents (Luke 14:32).