/man tis"euh/ , n.
1. Math. the decimal part of a common logarithm. Cf. characteristic (def. 3a).
2. Obs. an addition of little or no importance, as to a literary work.
[ 1860-65; mantisa addition, makeweight, said to be from Etruscan; logarithmic mantissa so called because it is additional to the characteristic or integral part (term introduced by H. Briggs) ]