< centre n. and adj. (or its source) + -oid suffix.
1. = centrode n. [In this sense introduced by Prof. A. B. W. Kennedy, 1876, on the analogy of cycloid and other names of curves, but subsequently abandoned for centrode.]
2. Centre of mass, or of gravity.
"The main features of this algorithm are isotope cluster identification, automated charge determination, generation of a theoretical isotopic abundance distribution, matching the theoretical and experimental isotopic abundance distributions, identification of other overlapping isotopic peak clusters, determination of improved accuracy of averaged centroid mass values, matching of assigned mass values to proteolytic or MS/MS fragment ions, and baseline plus S/N calculations using data between the isotopic peaks."
- Bogdanov and Smith, "Proteomics by FTICR mass spectrometry: top down and bottom up", Mass Spectrometry Reviews 24:168 (2005)
I think what they mean here is the averaged mass of all the isotopes, as opposed to the monoisotopic mass.