Miniscule is a variant of minuscule, meaning “very tiny.” Ants, grains of sand, and portion sizes at fancy restaurants might all be described as miniscule.
Mini- means small, as in the words minimal and miniskirt. That’s why it’s in the word miniscule too, right? Wrong. It’s there because enough people spelled the word incorrectly that dictionary editors have given in. The traditional spelling is minuscule, with a u instead of a second i; minuscule is derived from the Latin word minus meaning “less.” Sticklers are surely convinced that the newfangled spelling illustrates the miniscule amount of respect that English speakers have for their own language.