Definition of "trap-rock" [trap-rock]

• A rock consisting of trap; trap. (noun)

The Century Dictionary (Public Domain)

• "It comes from beneath the trap-rock, of which I shall have to speak when describing the geology of the entire country; and as it usually issues at a temperature of 72° Fahr., it probably comes from the old silurian schists, which formed the bottom of the great primeval valley of the continent."
• "In the middle was the caldron of the torrent, called the “Scarfe,” with the sheer trap-rock, which is green in the sunlight, like black night flung around it, while a snowy wreath of mist (like foam exhaling) circled round the basined steep, or hovered over the chasm."
• "The 16th of May saw us journeying over the plain which lies between Ugombo and Mpwapwa, skirting close, at intervals, a low range of trap-rock, out of which had become displaced by some violent agency several immense boulders."