Technical drawing terminology would be a good place to look for non-ambiguous terms, since it makes heavy use of all sorts of lines, and it’s following national standards which in turn are usually following international guidelines (general principles of presentation in technical drawings ISO 128).
This terminology appears to be fond of the term “trait” instead of “ligne”, but in everyday speech, they can be interchanged without a problem.
So here we go. Technical drawing distinguishes traits by their nature:
- trait continu (continuous line)
- trait interrompu (dashed line)
- trait mixte (long- & short-dashed lines)
... and by their thickness:
- trait fin (thin line)
- trait fort (thick line)
To which can naturally be added the intermediate trait médium (medium line), though it doesn’t appear to be part of the standards of technical drawing.
On this Wikipedia article I ran into trait mixte à deux tirets, which would be long-dash short-dash short-dash, so I guess one could use the model to generate fancy line descriptions if required:
- trait mixte à trois tirets (long-dash short-dash short-dash short-dash)
- trait mixte à deux traits longs (long-dash long-dash short-dash)
Strangely, dotted lines don’t appear to be part of the official terminology, though it is very commonly used in everyday life, obviously also in French.
- ligne pointillée (Dotted line)