unionserth

== Welsh == === Etymology === union (“straight, upright”) +‎ serth (“steep”). === Adjective === unionserth (feminine singular unionserth, plural unionserth, not comparable) perpendicular Synonym: perpendicwlar vertical Synonyms: fertigol, uwchbennol, unionsyth very steep === Further reading === R. J. Thomas, G. A. Bevan, P. J. Donovan, A. Hawke, et al., editors (1950–present), “unionserth”, in Geiriadur Prifysgol Cymru Online (in Welsh), University of Wales Centre for Advanced Welsh & Celtic Studies