the season between autumn and spring, the coldest part of the year, in the N hemisphere the months December, January, and February; = wintertime

Let no man boast … that he has got through the perils of winter till at least the seventh of May — Trollope

in astronomy, the period in the N hemisphere extending from the December solstice (shortest day of the year) to the March equinox (time when day and night are of equal length)