/ flem; NAmE / noun [ U ]
1.
the thick substance that forms in the nose and throat, especially when you have a cold
2.
the ability to remain calm in a situation that is difficult or upsetting
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WORD ORIGIN
Middle English fleem , fleume , from Old French fleume , from late Latin phlegma clammy moisture (of the body), from Greek phlegma inflammation, from phlegein to burn. The spelling change in the 16th cent. was due to association with the Latin and Greek.