From Longman Dictionary of Contemporary Englishhigh watermarkhigh watermarkespecially American English the high watermark of a particular process is its most successful time or achievement SYN high pointhigh watermark of Reagan’s presidency may prove to have been the high watermark of the US-Israeli alliance. → watermark
Examples from the Corpus
watermark of• Penal Policy in a Changing Society stands as the high watermark of what later became known as the treatment model. 