phlegm /flem/ BrE AmE noun [uncountable]
[ Date: 1300-1400 ; Language: Old French ; Origin: fleume , from Latin phlegma , from Greek , 'flame, phlegm' , from phlegein 'to burn' ]
1 . the thick yellowish substance produced in your nose and throat, especially when you have a cold SYN mucus
2 . unusual calmness in worrying, frightening, or exciting situations