Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
prae-longus, a, um, adj., very long (not in Cic. or Cæs.): homo, i. e. very tall, Quint. 6, 3, 67: gladii, Liv. 22, 46: cauda, Plin. 8, 33, 51, § 121: hasta, Tac. A. 6, 3: gracilitas, Plin. 13, 4, 9, § 46.
Of time, very long: sermones, Quint. 10, 3, 32.