Answer: caulked

AnswerCrossword Clue
CAULKED

Made watertight

CAULKED

Made airtight, as a window frame

CAULKED

Patched cracks with oakum.

CAULKED
Applied oakum to
CAULKED
Weather-stripped
CAULKEDWeatherproofed, in a way
CAULKEDSealed around windows, in a way
CAULKEDWeather-stripped, in a way
CAULKEDFilled in some gaps