From Longman Dictionary of Contemporary Englishsplitting headachesplitting headacheHURT/CAUSE PAINa very bad headache → splitting
Examples from the Corpus
splitting headache• Chapter Twelve Melissa slept late and awoke with a splitting headache.• I couldn't move my arms or legs, my body tingled all over and I had a terrible splitting headache.• They hold their heads tight when coughing because of the splitting headache.• What good can you do mooning around worrying, picking at your food like an anorexic, and giving yourself splitting headaches?• I realized that I had a splitting headache and that my knee joints were uncertain of their purpose when I stood up.• It allowed Nicholas a long, hard night's sleep, followed by a splitting headache in the morning. 