What's the meaning of “margin” in this context?

Question

The idiom by the skin of one's teeth is defined on Dictionary.com as:

by an extremely narrow margin; just barely; scarcely

What does margin mean in the above definition? I've looked it up on OALD and it defines it as: the amount of time, or number of votes, etc. by which somebody wins something. However, the thing that confuses me is, reading the origin of the idiom on http://www.phrases.org.uk/meanings/83000.html, the idiom seems to be usually used in regard to a narrow escape from a disaster, and that appears to have nothing to do with winning like it's defined on the definition of margin from OALD. Or does margin here in the definition mean something else?

Answer 1

A margin is, broadly, any edge or border. It may be physical, like the margins of a printed page—the white area around the edges where no printing appears; or it may be figurative. In figurative uses, such as those you cite, what is meant is the width of the ‘margin’ which separates one outcome from another.

• In business the margin of profit is the ‘distance’, measured in dollars or Euros or yen, between making a profit and suffering a loss. The marginal cost, or cost at the margin, is the additional cost of making one more purchase or manufacturing the final widget, the overhead costs having already been ‘sunk’ in making all the previous purchases or widgets.
• In a race, the margin of victory is the ‘distance’, measured in inches or centimeters, between the winner and the runner-up; in politics, the margin of victory is measured in votes.
• In adventures, the margin of escape is the ‘distance’, measured in whatever the relevant factor may be—inches or seconds or pips on playing cards—between suffering disaster and escaping it.

So to win “by the skin of your teeth” is to win by the narrowest possible margin: the thickness of the skin which covers your teeth, which of course has no thickness at all since no such skin exists.