Arabic defective verbs

I don't know anything about Arabic, so I can't really say. w:Defective verb does have a section on Arabic though. Does that describe what you mean?

No, that section describes actual defective verbs in the sense of missing parts of their conjugation, not in the sense of "having a weak final radical" (where "weak" here specifically means w or y). There's only a couple such verbs in Arabic missing parts of their conjugation. So yes the fact that "defective verb" can mean two different things is confusing and I suggest you go ahead and rename "defective" -> "final-weak" in all of the places I just mentioned. You can probably do this easier than I can.

But maybe it should be nominated at WT:RFM first?

Sure, go ahead.

Ok done.