jumping-off place is a noun meaning "a place from which an enterprise or expedition is launched". It carries one recorded sense.
a place from which an enterprise or expedition is launched
“one day when I was at a suitable jumping-off place I decided to see if I could find him”
“my point of departure was San Francisco”
Definitions, synonyms and semantic relations for jumping-off place come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.