This word refers to mass, volume, and size: "The steamship was of great bulk." It is also used to refer to the greater part of something (the bulk of mankind). The alternative to bulk in this second meaning is majority, a term which indicates or suggests counted numbers. It is permissible to refer to the bulk of the armed forces (mass, size, volume) but preferable to say "the majority of those present" rather than "the bulk of those present."
Dictionary of problem words and expressions. Harry Shaw. 1975.