The present participle of 'beal'; to suppurate, fester, or form pus-filled sores.
From Middle English 'beal' or 'bile,' related to Old English 'bȳl' (boil). The word comes from the concept of painful swelling that needs to drain.
Medieval and early modern doctors would describe wounds as 'bealing' when they were beginning to form infection—it's a delightfully specific word from medical history that nobody really uses anymore.
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