In your dictionary, "mayor" may first pop up as the comparative and superlative form of "grande" meaning "bigger; biggest; older; oldest," but it carries other meanings, too. For example, "al por mayor" means "wholesale." Listen to our featured song "Aparencias" ("Appearances"), where Héctor Montaner croons:
Si el amor me lo vendieran al mayor
If love were sold to me wholesale
pagaría lo que fuera por comprarlo
I would pay anything to buy it
Captions 5-6, Hector Montaner - AparienciasPlay Caption
Note that Montaner takes a little bit of poetic license by skipping "por": In your dictionaries, "vender al por mayor" is the full, correct way to say "sell wholesale."
Elsewhere in our videos, Francisco in Salamanca describes his campus as:
La Universidad Pontificia y la Universidad de la Experiencia, donde vamos los mayores.
The Pontifical University and the University of Experience, where we the elders attend.
Captions 7-8, Francisco Pérez - La UniversidadPlay Caption
At his school, mayores are defined as anyone 55 or older, but mayores can also simply mean "adults." You'll have to listen for the context to discern if mayores refers to ancianos, viejos y/o abuelos -- that is to say, the elderly -- or simply someone who's an adult, or of legal age.
If in doubt about the meaning of mayores (as a description or a comparison), heed this expression:
¡Más respeto con los mayores!
Be more respectful to your elders (and betters)!