A vacation taken during the winter period; often refers to year-end/new-year holidays (commonly used interchangeably with 'winter break').
大学は12月下旬から1月上旬まで冬期休暇がある。
The university has winter vacation from late December to early January.
冬期休暇中に家族と温泉旅行に行くつもりだ。
I plan to go on a hot-spring trip with my family during the winter break.
冬期休暇の宿題は早めに片付けておこう。
Let's finish the winter-break assignments early.