caulk

American  

[kawk] / kɔk /

Or calk

verb (used with object)

1. to fill or close seams or crevices of (a tank, window, etc.) in order to make watertight, airtight, etc.

2. to make (a vessel) watertight by filling the seams between the planks with oakum or other material driven snug.

3. to fill or close (a seam, joint, etc.), as in a boat.

4. to drive the edges of (plating) together to prevent leakage.

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noun

1. Also caulking a material or substance used for caulking.

caulk British  

/ kɔːk /

verb

1. to stop up (cracks, crevices, etc) with a filler

2. nautical to pack (the seams) between the planks of the bottom of (a vessel) with waterproof material to prevent leakage

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Other Word Forms

• caulker noun

Etymology

Origin of caulk

First recorded in 1350–1400; from Latin calcāre “to trample, tread on” (verb derivative of calx “heel”), conflated with Middle English cauken, from Old French cauquer “to trample,” from Latin calcāre, as above

Explanation

Caulk is a sealant. It comes in a tube and is used commonly by plumbers and carpenters trying to seal up cracks where air or water might push through. When a plumber caulks a tub, he's applying caulk to its seams to make it watertight. Caulk can be used to describe both the process of applying caulk and the sealant itself. The word caulk comes from the Old Northern French cauquer, meaning "to press down." After you lay the caulk down over the seam you press it down by either running your finger over it or using a specific tool to force the caulk to settle into the hole you're trying to cover.

Example Sentences

To answer those questions, the research team examined previously unstudied materials recovered with the vessel, including cordage and waterproofing caulk.

From Science Daily • Feb. 16, 2026

Radiocarbon testing of the cordage and caulk indicates the boat was built between the 4th and 3rd centuries BCE.

From Science Daily • Feb. 16, 2026

“They would come in and put some caulk on it,” he said.

From Seattle Times • May 28, 2023

To close the gaps between the molding miters and the wall, apply a thin line of paintable caulk.

From Seattle Times • May 12, 2023

“I can caulk it, and tarp it, which should keep the water out, but I think the boxes would be a lot safer back in the house.”

From "Storm Runners" by Roland Smith

Related Words

• block
• shut
• shutter