Noah Webster
Approximation
APPROXIMA'TION, noun
1. Approach; a drawing, moving or advancing near.
2. In arithmetic and algebra, a continual approach or coming nearer and nearer to a root or other quantity, without being able perhaps ever to arrive at it.
3. In medicine, communication of disease by contact.
4. A mode of cure by transplanting a disease into an animal or vegetable by immediate contact.