Which of the following is NOT a term for a tempo marking?

The term "brillante" is primarily used to describe a style of playing rather than a tempo marking. It indicates that the music should be played in a brilliant or spirited manner, often with a lively and energetic character. In contrast, the other terms listed have specific associations with tempo indications.

"Pianissimo" refers to playing very softly, marking a dynamic level rather than a tempo. "Accelerando" signifies a gradual increase in tempo, instructing the performer to speed up. "Allargando" means to play more broadly, often involving a slight slowing down of the tempo. Thus, "brillante" stands out as the term that does not fit the category of tempo markings, focusing instead on the expressive quality of the music.