I don’t mean, ‘what does it say on your vocab card?’; I mean, what does it mean more broadly than its use in the NT? In Benjamin Edsall’s Paul’s Witness to Formative Early Christian Instruction, he interestingly points out:
[There is an] absence of an analogous use of the term [that is, analogous to Paul’s use] in Greek literature, where it is used with a variety of meanings and only rarely in reference to a messenger of any kind. (p123)
As in Herodotus Hist. 1.21.4; 5.38.8; Plutarch Phoc. 11.1. Other meanings include an expedition (military and naval), a list of colonists and a colony in Dionysius of Halicarnassus Ant. rom. 7.5.3, 9.59.2; and 7.13.3 respectively. Note also the ‘sending’ of Jewish emissaries: Josephus A.J. 17.300. See Regstorf 1964, 407-408. (p123, n.7)
Perhaps, then, it might have meant something like ‘delegation’?? Of course, we don’t need to import that directly into the NT, as there the term is given contextual specification; but it’s interesting that the glosses we learn may lead us astray if we put too much weight on them or press them beyond the NT.