Definition of "underwood"

What improvement the stirring of the ground about the roots of Oaks is to the Trees I have already hinted; and yet in Copses where they stand warm, and so thickn’d with the under wood, as this culture cannot be practis’d, they prove in time to be goodly Trees.

1670, John Evelyn, Sylva, or A Discourse of Forest-Trees and the Propagation of Timber, London, Chapter 3, Of the Oak, pp. 16-17

[…] the Country near the Sea-side, and some few Miles further is full of short Under-wood, and thorny Shrubs, which tore our Cloaths to Rags […]

1743, Robert Drury, The Pleasant, and Surprizing Adventures of Mr. Robert Drury, during his Fifteen Years Captivity on the Island of Madagascar‎, London, page 30

‘Accordingly I hid myself in some thick underwood, determining to devote the ensuing hours to reflection on my situation.’

1818, [Mary Shelley], Frankenstein; or, The Modern Prometheus. […], volumes (please specify |volume=I to III), London: […] [Macdonald and Son] for Lackington, Hughes, Harding, Mavor, & Jones

But tenants may cut underwood, and take wood sufficient to repair the pales, hedges, and fences, and what is called by law plough-bote, fire-bote, and other house-bote.

1825, Laws relating to landlords, tenants, and lodgers - Volume 7, page 17

In cutting coppices the usual plan is to leave what is termed plashers where the underwoods are thin and require new wood; a far better plan is to plant young stuff, which is not only cheaper but makes much better underwoods.

1860, S. G. Finney, Hints to Landlords, Tenants, and Labourers, page 33