Thorough has 7 different meanings across 3 categories:
Adjective · Prep · Proper Noun
A furrow between two ridges, to drain off the surface water.
"The farmer plowed a thorough across the field's ridge to let the rainwater run off."
"The detective's thoroughness in gathering evidence made finding the culprit easy."
performed comprehensively and completely; not superficial or partial
"an exhaustive study"
"made a thorough search"
"thoroughgoing research"
without qualification; used informally as (often pejorative) intensifiers
"an arrant fool"
"a complete coward"
"a consummate fool"
"a double-dyed villain"
"gross negligence"
"a perfect idiot"
"pure folly"
"what a sodding mess"
"stark staring mad"
"a thorough nuisance"
"a thoroughgoing villain"
"utter nonsense"
"the unadulterated truth"
Painstaking and careful not to miss or omit any detail.
"The detective conducted a thorough search of the apartment, examining every corner and hiding place without missing a single clue."
In plain English: Thorough means doing something completely and carefully without missing any details.
"The detective conducted a thorough investigation to find any clues at the crime scene."
Usage: Use thorough as an adjective meaning painstakingly detailed when describing actions like cleaning or investigating. Do not confuse it with "thoroughbred," which refers specifically to a breed of horse, nor use it where the noun form is required for specific contexts involving drainage ridges.
Through.
"The rain had thoroughly soaked the ground, leaving it completely saturated."
A scheme devised in 17th-century England by Thomas Wentworth, 1st Earl of Strafford to establish absolute monarchy in England.
"The king implemented a thorough to centralize power and rule without parliament."
The word thorough comes from Old English þuruh, which originally meant "through" or "across." It developed its current meaning of being complete or detailed by evolving directly from the preposition that describes passing from one side to another.