The phrase "narrowest part" means the thinnest or slimmest section or point of something.
Sentences with «narrowest part»
The most beneficial about it is the fact that it can pass through narrow parts without inconvenience of changing the positioning of the stroller. (babystrollersellect.com)
bottom - up modeling a modeling approach that arrives at economic conclusions from an analysis of the effect of changes in specific parameters on narrow parts of the total system (ipcc.ch)