Sibbens definition: (medicine) A <a>contagious</a> <a>disease</a>, once <a>endemic</a> in <a>Scotland</a>, resembling the <a>yaws</a> and marked by <a>ulceration</a> of the <a>throat</a> and <a>nose</a> and by <a>pustules</a> and soft <a>fungous</a> <a>excrescences</a> upon the surface of the body.