(Internet slang) a “sickness” in teenagers characterized by sophomoric, edgy, and/or pretentious behavior (trying too hard to be special in unusual ways)

characterized by such behavior

podiatrist

psychopathy

(dentistry) periodontitis

(pathology) collagenosis, collagen disease

(fiction) Hanahaki, an illness affecting those consumed by unrequited love that manifests as the coughing up of flowers, which clears up upon reciprocation. A fictional illness, it has found popularity among both Japanese and foreign online fanfic (especially) artists and authors for its poetic quality.

(literally) know the other side and yourself, a hundred battles will not be perilous

(idiomatic) Speak no ill-fated words; let no feeding cause you ailment; literally Diseases enter through the mouth, disasters come out of the mouth.