a mixture in which one thing (typically a solid) is dispersed in (spread out among the molecules of) another thing (typically a liquid solvent) but not truly “dissolved.” For something to be dissolved, each molecule has to be completely surrounded by the solvent, but in a suspension it’s more like you have small clumps of the suspended thing and they’re kinda “floating” – if allowed to settle (often with help from centrifuging) they will eventually separate from the liquid, but then they can be re-dispersed by agitation (shaking, inverting the tube, swirling, etc.)