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What Does "Full Bore" Mean?

Bryce Clinton
Bryce Clinton

The English saying, full bore, means to the fullest extent possible, as in "To win the war, each soldier had to fight full bore." It also means to do something completely or thoroughly, such as "It was a full bore investigation that utilized every detective in the police force." Additionally, it can mean to move at the greatest possible speed or with the most power, as in an automobile traveling at top speed. Great force or effectiveness are usually implied.

The expression can be used as an adjective, an adverb, or a noun. In each case, its meaning reflects full capacity or power. It has traditionally been a British idiom, but it is now more widely used in English throughout the world. It is defined by most dictionaries.

A full-bore weapon may be a large caliber, or loaded to capacity with gun powder and ammunition.
A full-bore weapon may be a large caliber, or loaded to capacity with gun powder and ammunition.

The etymology of full bore can be traced to its use as a measurement of the diameter of a cylinder. This sense comes from the word bore, as in to bore, auger, or drill a hole. There has been some speculation as to whether this use as a measurement of a cylinder can first be attributed to engines or rifles, but consensus points in the direction of rifles.

In its reference to firearms, bore is a synonym for caliber; thus, a full-bore weapon is either larger, or loaded to its full capacity with gun powder and ammunition. Such a weapon might have a wider barrel, larger bullets, and be more powerful than a small-bore weapon. Here, small bore is the opposite of full bore; however, the evolution of small bore as an expression has taken a different route and it has come to mean trivial, trifling, or provincial. The two expressions are only antonyms when they specifically reference weapons.

In the sense of measuring the cylinder of an engine, full bore refers to a completely open cylinder operating with maximum fuel and moving at top speed, as with an unchoked carburetor. It may also refer to piston diameter and the boring of an engine for more power. Both roots for the idiomatic expression lead to its modern meaning and usage, pointing to the greatest capacity of force, power, or execution.

Many of the synonyms for full bore are also idiomatic expressions. With reference to moving at top speed, these idioms include the following: full throttle, full speed, flat out, and all out. When referring to the fullest extent possible, or operating at full capacity, the idiom "no holds barred," which means without restriction or limitation, is another synonym.

Discussion Comments


So I guess this phrase is used a lot in the military. I think I've only come across it a couple of times in news articles, again talking about military missions.

But my brother says he has heard it many times referring to the piston in car engines. He's a big car buff and apparently, a bigger bored engine and a full bore valve means that the engine is more powerful. The current meaning of full bore actually makes a lot more sense when it's used to talk about cars. Much more than the diameter of a pipe anyway. But this is just my opinion.

In day to day life, I never say full bore. I usually say full throttle or full force when talking about maximum speed and power.


This idiom seems very similar to another one: "going in with both barrels loaded" which means to do something forcefully. "Loaded for bear" is another related one, which basically means the same thing.

Looking at the origin of "full bore," I think it might have meant "full capacity" initially and then over time, also meant full speed or full power. Because if you think about it, a bore is the diameter of a pipe. And full bore would mean something that fills up or takes up all of the space of that pipe. So it's using all of the capacity. I guess with the emergence of firearms, the meaning was expanded to also mean fast and powerful.

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    • A full-bore weapon may be a large caliber, or loaded to capacity with gun powder and ammunition.
      By: BestPhotoStudio
      A full-bore weapon may be a large caliber, or loaded to capacity with gun powder and ammunition.