Noun
TRGB (countable and uncountable, plural TRGBs)
(astronomy) Initialism of Tip of the Red Giant Branch.; A classification of stars on the Hertzsprung-Russell diagram for all stellar populations or of a given sample set, the end of the plot for stars existing on the red giant branch as it branches off from the main sequence.
Coordinate terms: star, red giant, red giant star, giant star, red giant branch