godan verb (-ku), intransitive verb
Rare verb for coughing; the more common word is 咳をする (せきをする). This form is literary or old-fashioned.
See also: 咳
彼はしきりにせいた。
He coughed repeatedly.
Rare kanji spelling; the verb is almost always written in kana as せく.
Standard kana spelling; the kanji form 咳く is rarely used.
The noun 'cough'; 咳をする is the standard way to say 'to cough'.
The verb せく is a rare, older form related to the noun 咳 (せき, 'cough'). The exact derivation is uncertain.