dog day
noun
1
a
dog days plural : the period between early July and early September when the hot sultry weather of summer usually occurs
b
: a day in dog days : a hot sultry day
2
dog days plural : a period marked by dull lack of progress
the dog days following any major upheaval
Word History
Etymology
back-formation from dog days, translation of Late Latin dies caniculares, translation of Greek hēmerai kynades; from their being reckoned in ancient times from the heliacal rising of the Dog Star (Sirius)
First Known Use
1538, in the meaning defined at sense 1a