any unwanted and destructive insect or other animal that attacks food or crops or livestock etc.; "he sprayed the garden to get rid of pests"; "many pests have developed resistance to the common pesticides"
a persistently annoying person
any epidemic disease with a high death rate
a serious (sometimes fatal) infection of rodents caused by Yersinia pestis and accidentally transmitted to humans by the bite of a flea that has bitten an infected animal