WordNet sense 1 ((computer science) the processing time required by a device prior to the execution of a command):

command processing overhead time, command overhead, command processing overhead

WordNet sense 2 (the expense of maintaining property (e.g., paying property taxes and utilities and insurance); it does not include depreciation or the cost of financing or income taxes):

operating expense, budget items, operating cost

WordNet sense 3 ((computer science) the disk space required for information that is not data but is used for location and timing):

disk overhead

WordNet sense 4 (a transparency for use with an overhead projector):

viewgraph

WordNet sense 5 (a hard return hitting the tennis ball above your head):

smash