/op"euh ray'ting/ , adj.
1. used or engaged in performing operations: an operating surgeon.
2. of, for, or pertaining to operations: an operating budget.
3. of or pertaining to the proper operation of a machine, appliance, etc.: a manual of operating instructions.
4. Railroads. of, pertaining, or belonging to railroad workers, as engineers or firemen, who are directly engaged in the mechanical operation of trains: an operating union.
[ 1800-10; OPERATE + -ING 1 ]