From Longman Dictionary of Contemporary Englishhigh tideˌhigh ˈtide noun 1 [countable, uncountable]DNTTW the point or time at which the sea reaches its highest level OPP low tide High tide is at seven in the morning.at high tide The waves became much more powerful at high tide.2 [singular]BEST the time when something is at its best or most successful the high tide in the party’s fortunes
Examples from the Corpus
high tide• Yet the high tide of nationalism was still to come, from two World Wars and the colonial revolution. 