Primarily seen in place name transliterations: 喀布尔 (Kabul), 喀什 (Kashgar), 喀麦隆 (Cameroon). As an onomatopoeia, it represents a harsh coughing or retching sound.
口 (the mouth radical) marks 喀 as a sound issuing from the mouth. It groups this onomatopoeia with 哈, 呵, 啊, 嗯 and the rest of the speech-and-breath family — every cough, gasp and exclamation that needs a 口 anchor.
客 kè gives the sound, with the tone shifted to kā for the cough-noise effect. The phonetic also serves transliterations — 喀什 (Kashgar) and 喀麦隆 (Cameroon) both ride this kā reading, separate from the cough sense.