multiplet 

https://doi.org/10.1351/goldbook.08379
Feature in a nuclear magnetic resonance spectrum that is split but is too complex to easily interpret.
Note:
A multiplet is distinguished from multiplicity of NMR peaks that give well-resolved doublet, triplet, quartet, quintet etc.
Source:
PAC, 2021, 93, 647. (Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)) on page 697 [Terms] [Paper]