v. [UNDER-1 4 a.] trans. or intr. To undermine; spec. (in coal-mining), to undercut. Also Underholing vbl. sb.
1398. Trevisa, Barth. De P. R., XIII. xix. (Bodl. MS.). Vnder hoolinge and vnder crepinge and wastinge vnder brymmes is icleped Alluuio.
1891. Cent. Dict. (as U.S. mining term).