A French horn is a musical instrument of the brass family. It is shaped like a long metal tube with one wide end, wound round in a circle. You play the French horn by blowing into it and moving valves in order to obtain different notes.
French horn in British English
noun
music
a valved brass instrument with a funnel-shaped mouthpiece and a tube of conical bore coiled into a spiral. It is a transposing instrument in F. Range: about three and a half octaves upwards from B on the second leger line below the bass staff
horn
French horn in American English
a brass instrument with a mellow tone, consisting of a long, spiral tube ending in a flaring bell, three valves, and a funnel-shaped mouthpiece: horn is the term preferred by musicians playing classical music