Synonyms and related words :
abrupt, acmatic, apical, arrowlike, azimuth circle, bluff, bold, bolt upright, breakneck, capital, chief, consummate, dead straight, direct, downright, erect, even, flat, head, headlong, headmost, highest, horizontal, in a line, level, lineal, linear, maximal, maximum, meridian, meridional, normal, orthodiagonal, overmost, paramount, perpendicular, plumb, plunging, precipitous, preeminent, rampant, rapid, rearing, rectilineal, rectilinear, right, right angle, ruler-straight, sharp, sheer, smooth, stand-up, standing up, steep, straight, straight-cut, straight-front, straight-side, straight-up, streamlined, summital, supreme, tip-top, top, topmost, TRUE, ultimate, unbending, unbent, unbowed, unbroken, uncurved, undeflected, undeviating, undistorted, uninterrupted, unswerving, unturned, up-and-down, upended, upmost, uppermost, upraised, upreared, upright, upstanding, vertical circle, zenithal