the principal part of a duet (especially a piano duet)
"In their piano duo performance, Sarah played the primo while her partner handled the accompaniment."
The principal part of a duet.
"In their jazz arrangement, the saxophone takes the primo line while the trumpet plays softly in the background."
the best of its kind
"After trying dozens of restaurants, we finally found a primo spot for authentic Italian pasta in the old town."
Best; first-class.
"She insisted that their new restaurant was primo, praising its fresh ingredients and friendly staff."