Hoodoo. Landform. A (usually thin) spire of rock made of soft, erodible rock, but topped with a harder rock that protects the top from erosion. Hoodoos typically have an irregular shape. Link to Wikipedia for details.
Around Las Vegas, look for hoodoos formed of fanglomerate rock along Lake Mojave below the town of Nelson and along Kyle Canyon Road on the eastern flanks of Mt. Charleston.