Part of speech : Verb

Definition: is to show suppressed anger, hate, or jealousy

Source: Merriam Webster Dictionary

Found In “Choi Jeong Min” by Franny Choi, “boneless rumor smoldering behind the curtain
& speaking through an ink-stained puppet? Line 13-14

By rereading the sentence with the definition made more sense because it is most likely describing the feeling or emotions towards of an object.