moat

American  

[moht] / moʊt /

noun

1. a deep, wide trench, usually filled with water, surrounding the rampart of a fortified place, such as a town or a castle.

2. any trench, such as one used for confining animals in a zoo.

3. a competitive advantage a business has in its field.

   The company's moat was reduced when the patent on the devices they sold expired.

---

moat British  

/ məʊt /

noun

1. a wide water-filled ditch surrounding a fortified place, such as a castle

---

verb

1. (tr) to surround with or as if with a moat

   a moated grange

Etymology

Origin of moat

First recorded in 1325–75; Middle English mote, from Old French: “clod, mound,” of obscure origin

Explanation

Not many houses these days have a moat — it's a trench dug outside a castle and is usually full of water. A moat means "Keep out!" You're most likely to hear about moats if you read a fairy tale or a history of medieval times. This water-filled ditch is one of the lines of defense for a castle. In the old days, it was pretty effective. If you filled the moat with a deadly fish — like a piranha — that was an even better defense. A moat is pretty much the opposite of a welcome mat.

Example Sentences

In the decades since then, it has become clear that Montezemolo’s innovation dug a moat around the company that no competitor has been able to cross.

From The Wall Street Journal • Apr. 10, 2026

“Not that many companies out there that have this kind of moat, which is a global wallet that everyone recognizes.”

From Los Angeles Times • Apr. 3, 2026

"It's got no moat but it has got a little railway I can drive around," he said.

From BBC • Mar. 28, 2026

The tilted-over towers overlooking the palace moat have all been brought back upright, and workers are building new brick castellations for their supporting ramparts.

From Barron's • Mar. 26, 2026

The ice crackled in the puddles and on the gelid moat.

From "The Once and Future King" by T. H. White

Related Words

• gully
• trench