Melisma is a musical term used to describe the technique of singing a single text syllable — like "love" — while moving between several different notes in succession.
Melisma, often referred to as "riffing," is a common technique in rhythm and blues. You'll hear it in other types of music, too, including pop, opera, and gospel music. Melisma is often used to showcase a singer's agility and range, or to add flair to a song. You'll sometimes hear singers using melisma on words like "brave" and "free" when singing the U.S. national anthem. The opposite of melisma is syllabic singing, where each syllable of a word gets just one note — think "Twinkle, Twinkle, Little Star."