Fast has 23 different meanings across 6 categories:
A train that calls at only some stations it passes between its origin and destination, typically just the principal stations
"The emergency room doctor ordered a FAST scan to quickly check for internal bleeding after the car accident."
The act or practice of abstaining from food or of eating very little food.
Initialism of Focused assessment with sonography for trauma.
In plain English: A fast is an annual religious day when people stop eating certain foods to show respect and reflect on their actions.
"The fast is often observed for religious or spiritual reasons before major festivals."
Usage: Do not use "fast" to mean Focused assessment with sonography for trauma; instead, refer to this medical procedure by its full acronym or the standard term FAST exam. The word fast as a noun exclusively describes an act of abstaining from food for religious, spiritual, or health reasons.
abstain from certain foods, as for religious or medical reasons
"Catholics sometimes fast during Lent"
To restrict one’s personal consumption, generally of food, but sometimes other things, in various manners (totally, temporally, by avoiding particular items), often for religious or medical reasons.
"After consulting his doctor about the kidney stones, he decided to fast from all solid foods until the procedure was scheduled."
In plain English: To fast means to stop eating and drinking for a specific period of time.
"The food was cooking too fast, so I turned down the heat."
Usage: As a verb, to fast means to voluntarily abstain from eating or drinking, usually for a specific period of time. You would use this word when describing someone who is intentionally skipping meals, such as "He decided to fast before his surgery."
acting or moving or capable of acting or moving quickly
"fast film"
"on the fast track in school"
"set a fast pace"
"a fast car"
(used of timepieces) indicating a time ahead of or later than the correct time
"my watch is fast"
unrestrained by convention or morality
"Congreve draws a debauched aristocratic society"
"deplorably dissipated and degraded"
"riotous living"
"fast women"
unwavering in devotion to friend or vow or cause
"a firm ally"
"loyal supporters"
"the true-hearted soldier...of Tippecanoe"
"fast friends"
Firmly or securely fixed in place; stable.
"The heavy shelf was screwed so fast to the wall that it didn't wobble when I leaned on it."
In plain English: Fast means moving very quickly or happening in a short amount of time.
Usage: Use "fast" to describe something that is firmly attached, secure, or unmovable, such as a knot tied fast or an object bolted fast. Do not use it to mean quick or speedy when referring to speed, as that is the primary everyday distinction from "fixed."
quickly or rapidly (often used as a combining form)
"how fast can he get here?"
"ran as fast as he could"
"needs medical help fast"
"fast-running rivers"
"fast-breaking news"
"fast-opening (or fast-closing) shutters"
In a firm or secure manner, securely; in such a way as not to be moved; safe, sound .
"The old anchor was fastened so securely that even the fiercest storm couldn't move the ship."
In plain English: Fast means moving at a very high speed.
"The car was moving fast down the highway."
Usage: Use "fast" as an adverb to mean moving at high speed, such as running fast, rather than the archaic meaning of being firmly fixed. Do not use it to describe something that is securely attached or unmovable in modern conversation.
Short for "stand fast", a warning not to pass between the arrow and the target
"The archer shouted, "Fast!" as he released his shot, commanding me to stay put rather than move into the line of fire."
A surname.
"My neighbor, Mr. Fast, invited me over for dinner last night."
The word "fast" comes from Old English fæst, meaning "firm" or "secure." Over time, its meaning shifted to describe something done with speed, likely because a secure grip allows for rapid movement.