Define Mano A Mano Meaning

The term is Spanish and literally means "Hand to Hand" as in unarmed combat. However in its modern incarnation the term is used in any scenario where two (usually male) individuals are going to have some sort of competition. Eg Darts, Snooker, an actual fight, even videogames. It is rarely a serious threat.

mano a mano; mano mano; man mano

As far as Italians are concerned these expressions (freely exchangeable) have only one use and meaning, the origin of which - most likely - has to do with the way in old times people used to measure short distances by using an open hand.
You put a hand widely open beside another end moving on as you take measures. From this habit in old times may have arisen the idea of following an event - shal we say - "step-by-step" (if you're measuring long distances) ... or similarly "hand-by-hand" (if you're measuring, say, a cloth or a stick of wood, etc.).
By extension, every time an Italian wants to mean following something very closely and at every new event uses this expression.
I mark on the wall my child's height as (mano a mano) he grows.

A Portuguese expression to describe a fight between two people

This expression could come either from italian or spanish, it literally means "hand to hand" and it is used to indicate an argue, a verbal fight between two people.

Yet another humerous film quip has sailed over the heads of the gibbering, slack jawed, troglodytes to enter the vernacular, sans humor.
"mano y mano" is Spanish for hand AND hand. Used for comedic effect, to imply mental simplicity, in several films. (Other variants include "mono y mono", Spanish for monkey and monkey = malapropism el mejor)
("MANO A MANO" is Spanish for hand TO hand - combat...
This is the actual phrase that is so often mutilated)

"He dun call me ig'nint!"
"Reeallly, ignorant of what? Where would one start."

Spanish for "hand-to-hand". Used most commonly for a competition between two people - often in hand to hand combat.

The phrase is often mistakenly thought by English speaking people to mean "man-to-man".

man to man, one on one, usually used in the context of a physical confrontation / altercation between two gentlemen.

"mano y mano" is Spanish for Hand to hand. Usually associated in engaging in throwing fisticuffs with two or more people, usually two.

Is layman's terms, a fight, but not usually followed closely to it's meaning. Often times, swords, or other weapons, not involved with guns or firearms, are associated with the term.