What does "millimetre" mean?

An SI/MKS unit of measure, the length of ¹⁄₁₀₀₀ of a metre. Symbol: mm

Millimetre

Common synonyms include: millimeter, millimetre wave, millimetre-based, millimetre-related, millimetre-scale, millimetre-sized.

The exchange unfolding in front of my eyes had not a single millimetre of a gap in which for me to slip.

noun

noun ·4 syllables ·Rare ·Advanced level

Noun

1
An SI/MKS unit of measure, the length of ¹⁄₁₀₀₀ of a metre. Symbol: mm
"Holonyms: centimetre < decimetre < metre < kilometre < megametre < gigametre < terametre < petametre"
2
a metric unit of length equal to one thousandth of a meter wordnet

"The exchange unfolding in front of my eyes had not a single millimetre of a gap in which for me to slip."

From French millimètre, equivalent to milli- + metre.