trom ‧ bone /trɒmˈbəʊn $ trɑːmˈboʊn/ BrE AmE noun [countable]
[ Date: 1700-1800 ; Language: Italian ; Origin: tromba 'trumpet' ]
a large metal musical instrument that you play by blowing into it and sliding a long tube in and out to change the notes
—trombonist noun [countable]