flood tide is a noun meaning "the highest point of anything conceived of as growing or developing or unfolding". It carries 2 recorded senses.
the occurrence of incoming water (between a low tide and the following high tide)
“a tide in the affairs of men which, taken at the flood, leads on to fortune”
Definitions, synonyms and semantic relations for flood tide come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.