Webster's Revised Unabridged Dictionary · 1913

Melody

Melody , noun

[Old English melodie, French mélodie, Latin melodia, from Greek {not transcribed} a singing, choral song, from {not transcribed} musical, melodious; me`los song, tune + {not transcribed} song. See Ode.]

1.
A sweet or agreeable succession of sounds.
Lulled with sound of sweetest melody. — Shakespeare
2.
(Music) A rhythmical succession of single tones, ranging for the most part within a given key, and so related together as to form a musical whole, having the unity of what is technically called a musical thought, at once pleasing to the ear and characteristic in expression.

Melody consists in a succession of single tones; harmony is a consonance or agreement of tones, also a succession of consonant musical combinations or chords.

3.
The air or tune of a musical piece.