Synonyms for Ebb (same or very similar meaning)
WordNet sense 1 (a gradual decline (in size or strength or power or number)):
wane, ebbingWordNet sense 2 (the outward flow of the tide):
refluxWordNet sense 3 (flow back or recede):
ebb away, ebb down, ebb off, ebb outFrom the ODE community, based on WordNetadd/edit