I'm looking for the term (jargon) that used in music or orchestra and says where the singer stops singing and lets the orchestra playing instrumentally. What's it called?
You can use
tutti (Italian for “all”) to describe the sections where the ensemble plays without the soloist, the complement being, unsurprisingly, solo (Italian for “alone”) to describe the sections where the soloist performs alone or with accompaniment. Orchestral parts will have the words solo & tutti written to designate parts where the ensemble accompanies the soloist (solo) as opposed to where the band plays together with or without the soloist (tutti). You can use the term as a normal noun, e.g. At the tutti the winds continue the soloist’s line or Let’s go from the tutti after letter G.
An older term that you may also see, in music of the Baroque period, is
ripieno (form the Italian for “padding”) which designates passages for the whole band rather than the smaller, accompanying or solo ensembles (the “concertino”). In the player parts you might see the instructions con rip. or con ripieno (“with the ripieno”) for the tutti passages & senza rip./senza ripieno or conc/concertino for the passages where the concertino plays alone or accompanying a soloist. That said, in music of the period composers would also use solo/tutti to convey the same meaning as senza rip/con rip. Note, however, that ripieno more properly describes the ensemble rather than the passage of music.
Another old term is
ritornello, which is used in the context of Baroque opera or concerti grossi to designate a returning passage. It describes a returning, tutti section coming after a solo interlude. This is probably the specific word you're looking for, but it does describe a compositional device used in the Baroque period & isn’t much used in contexts outside of music of that period.
Besides these, i can’t recall any single musical term that describes your exact circumstance. You could call an extended orchestral section after the soloist ends an