noun, plural: spindles
(1) A collection of minute fibers composed of microtubules, which are prominent during cell division, as mitotic spindle or ”mitotic apparatus”.
(2) A specialized innervated muscle structure involved in the reflex action and in proprioception, as muscle spindle.
(3) A species of a poisonous shrub or small tree of the genus Euonymus, originally used for making spindles used for spinning wool.
(4) An EEG waveform that occurs during sleep, as sleep spindle.
Word origin: Middle English spindel, alteration of Old English spinel.