enzymes that cleave monomers (sometimes also di- or oligomers) from one end of a polymer chain. Exonucleases are able to cleave nucleotides, one by one, from either the 5- or the 3- (or both) ends of nucleic acids.
Source:
PAC, 1992, 64, 143. 'Glossary for chemists of terms used in biotechnology (IUPAC Recommendations 1992)' on page 153 (https://doi.org/10.1351/pac199264010143)