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ground floor

1 ENTRIES FOUND:
ground floor noun
plural ground floors
ground floor
noun
plural ground floors
Britannica Dictionary definition of GROUND FLOOR
[count]
: the floor of a building that is at ground level
called also (US) first floor

in on the ground floor

◊ If you are/get in on the ground floor of something (such as a new business or project), you become involved in it at the very beginning.