Definitions
from The American Heritage® Dictionary of the English Language, 4th Edition
 n. The least possible quantity or degree.
 n. The lowest degree or amount reached or recorded; the lower limit of variation.
 n. A lower limit permitted by law or other authority.
 n. A sum of money set by a nightclub or restaurant as the least amount each patron must spend on food and drink.
 n. Mathematics The smallest number in a finite set of numbers.
 n. Mathematics A value of a function that is less than any other value of the function over a specific interval.
 adj. Of, consisting of, or representing the lowest possible amount or degree permissible or attainable.
from Wiktionary, Creative Commons Attribution/ShareAlike License
 n. The lowest limit.
 n. The smallest amount.
 n. A period of minimum brightness or energy intensity (of a star).
 n. A lower bound of a set which is also an element of that set.
 n. The smallest member of a batch or sample or the lower bound of a probability distribution.
 adj. To the lowest degree.
from the GNU version of the Collaborative International Dictionary of English
 n. The least quantity assignable, admissible, or possible, in a given case; hence, a thing of small consequence;  opposed to
maximum .
from The Century Dictionary and Cyclopedia
 n. The smallest amount or degree; the least quantity assignable in a given case: opposed to maximum; in mathematics, that pointwhere a function has a less value than for any neighboring values of the variable.
 Of the smallest possible amount or degree; least; smallest: as, a minimum charge.
 Indicating or registering the lowest quantity or degree: as, a minimum thermometer.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
 n. the smallest possible quantity
 adj. the least possible
 n. the point on a curve where the tangent changes from negative on the left to positive on the right
Etymologies
Examples

There are some misconceptions about the use of the term minimum unit pricing...
Telegraph.co.uk  Telegraph online, Daily Telegraph, Sunday Telegraph

As a measure that everyone could recognize, clinicians and researchers used the minimum amount of drug needed to kill bacteria, expressed as milligrams of drug per liter of blood, which they called the minimum inhibitory concentration, or MIC for short.

There is what we call a minimum equipment list of a certain number of oxygen canisters that are required for every size of every airplane.

In a report titled “The Endgame,” the VPC offered what they described as minimum standards.

Mngadi said tribal communities would no longer be satisfied with what he described as minimum royalties.

There are no jobs hiding away in corners, and what jobs there are when you've got little experience and no qualifications are short term minimum wage jobs that may well see you off the dole for a few months before being dumped back.

The Israeli organizations assess that the workers were defrauded of at least 2. 25bn dollars in today's prices, in what they describe as a minimum and "very conservative" estimate of the misappropriation of the funds.

The Israeli organizations assess that the workers were defrauded of at least $2. 25bn in today's prices, in what they describe as a minimum and "very conservative" estimate of the misappropriation of the funds.

Our pricing at retail for brewer products we run what we called minimum advertised pricing policy.

As far as I am concerned, what we call a minimum wage is in fact starvation wage, a kind of semislavery endured only by those who have no other options, except perhaps to turn to crime.
oroboros commented on the word minimum
An especially small Englishwoman? (from BC cartoon  Wiley's Dictionary)
October 20, 2011