a. (UN-1 7 b.)
1865. Carlyle, Fredk. Gt., XVIII. ii. VII. 113. ‘Difficult, not undoable,’ persists the King.
190[?]. Evelyn Gladys, Shoes, Pigs and Problems, 7. After looking carefully at the problems which people are trying to solve, I find that a problem is to do things in an ‘undoable way.’
