1. A hollow or natural passage under or into the earth; especially, one with an opening to the surface.
2. A geological formation consisting of an underground enclosure with access from the surface of the ground or from the sea.
3. A storage cellar; especially, for wine.
4. When used as a verb, "to cave" means "to explore natural caves".

A naturally occurring underground hollow or passage; especially, one with an opening to the surface of the earth. Caves can form through a variety of processes, including the dissolution of limestone by flowing water, the differential cooling of volcanic magma (which occurs when the outside surface of the lava cools, but the inside continues to flow downwards, forming a hollow tube), or the action of wind and waves along a rocky coast.

Beware!

Look out, be careful!

Living in subterranean caves or passages.

An enclosed space or cavity in an organ or a part of the body.

Beware the man of [with] one book.

Be careful of the person who owns just one book.

“Beware the dog”.

This warning was used in Roman times and may be seen even now on some gates, at least in Europe. Would anyone be warned sufficiently in the United States if he or she saw this sign on a gate?

Beware of the dog!

An inscription found in a vestibule in the remains of Pompeii and now even on some modern gates; especially, in europe.

Beware what you say, when, and to whom.

Certainly good advice for all of us; especially, when writing e-mail. Recent studies have shown that e-mail messages may stay recorded somewhere for years and be available for others to read long after we thought they no longer existed.

A case in point is Bill Gates whose videotaped deposition for the federal trial in the United States revealed that he couldn't remember sending an e-mail about Microsoft’s plans to use Apple Computer to "undermine Sun".

Reading about, "The Tale of the Gates Tapes" in the November 16, 1998, issue of Time, the writer Adam Cohen, wrote, "Trouble was, it was a difficult line to swallow. Gates as a fuzzy-headed amnesiac? This is the man revered even by the geniuses who roam Microsoft’s Redmond, Washington, campus for his awesome 'bandwidth' (geekspeak for intelligence)."

Translation: "Beware of the silent dog and still water."

A Latin idiom: "Stagnant water can poison you." "Silent dogs can bite." Some Romans believed that taciturn (uncommunicative) adversaries were more dangerous than the ones who made a lot of noise.

1. A prehistoric or primitive human who lived in a cave, or caves.
2. Someone who lived in a cave; especially, a prehistoric human of the Paleolithic period.
3. Informal usage refers to a man who is crude or brutal, especially toward women.