Hæm"a*to*blast` (-blăst`), n. [Hæmato- + -blast.] (Anat.) One of the very minute, disk-shaped bodies found in blood with the ordinary red corpuscles and white corpuscles; a third kind of blood corpuscle, supposed by some to be an early stage in the development of the red corpuscles; -- called also blood plaque, and blood plate.