Meaning approximatly "fear(s) nothing", the word first came into use as a name for a class of large (sail) ships, dominant during the early 20:th century. The word has often appeared (occationally with slight difference in spelling, e.g. Dreadnaught).

Examples of modernised usage include (different, fictional) classes of ships, especially spacecraft within various sci-fi franchises, Spacemarine Dreadnoughts from GW:s Warhammer 40K franchise (sarcophagus-like warmachines which hold the remains of fallen, near-incapacitated heroes of the Imperium) and a guitar body. The word also commonly appears as a synonym for just about anything "big" or, in some cases, strong, impressive of awe-inspiring.

When you eat dirt for the first time and leave your family to build a shack in the woods

one that is among the largest or most powerful of its kind

One that is among the largest or most powerful of it's kind

A heavily armed sarcophagus of one of the Imperiums finest warriors.

A dreadnought was a type of battleship that emerged in the early 20th century. It all started in 1906, when the Royal Navy launched HMS Dreadnought. With its steam turbine engine, and uniform “all big gun” battery, its design was so superior that it made literally every other battleship in the world completely obsolete. The USA, UK, Germany, France, Italy, Japan, Russia, Spain, the Austro-Hungarian Empire, and even Chile, Brazil and Argentina frantically began building and buying ships of this type, which collectively became known as “dreadnoughts”. This “dreadnought race” is comparable to the nuclear arms race of the Cold War. Dreadnoughts were enormously expensive, and a nation’s technological, economic and industrial power was measured by how many dreadnoughts it possessed. Dreadnoughts ruled the waves up until WWII, when the age of battleships in general came to an end. Aircraft carriers and naval aviation superseded them as the key striking power of a modern fleet.

A turd of gargantuan proportions.