splitting
From Longman Dictionary of Contemporary Englishsplittingsplit‧ting /ˈsplɪtɪŋ/ adjective → splitting headacheExamples from the Corpussplitting• We passed a gaunt-looking man with splitting boots and a battered overcoat fastened with a string.• I realized that I had a splitting headache and that my knee joints were uncertain of their purpose when I stood up.• Then the crack of splitting wood, and the silence across the river shot out of the dark.