plural heydays
: the time when someone or something is most successful, popular, etc.
—usually singular
In the heyday of big cars nobody cared how much gas cost.
That's when he was in his heyday.
Cite this Entry
“Heyday.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/heyday. Accessed 23 Jun. 2026.
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