ПЫЛЬ _|_ DUST / PYL [pɨlʲ]
Hint with an alternative definition: it is a mild pollutant (non-toxic in the most cases) which piles up as time passes in the air or on a surface; a puff of dust contains plenty of pale particles, microbes, spores, flakes, a peel from a skin; so you need in an air filter. For example, imagine an old parlor with piles of books, carpets, pillows, no laugh, no peal of bells, the dust is everywhere… or imagine a beatiful pearl in the dark sea as an anti-dust because dust is like a powder of past & ill with no pulse of life.
Hints with translation + consonant words (by sounds or letters): it is like a pale silt or flour in the air / it is like a cloud of little pills
Hint with composition: pollen + idle, dull, feeble
Hint with a mirror: leap (a lot of action) | пыль (no action)
Russian tip: пыл (действие, активность) > пыль (смягчение действия, конец) / плавает в воздухе
Mental visualization: ПЫ (clean door and carpet) … ЛЬ (a lot of time has passed, the door squinted, in a web, and the carpet is half in dust) = dust as an indicator of stagnation