A secondary menu available through another menu, especially one that branches off the first.(noun)
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Use "submenu" in a sentence
"They also include the small arrow graphics that indicate that a submenu is present."
"The submenu is correct according to the guidelines …"
"Instead of being applied to the main window, those functions now do the same as the corresponding functions in the "This Frame" submenu, which is a more intuitive "context" for the context menu."