Synonyms and related words :
adamant, adamantine, aloof, arrowlike, cast-iron, constant, dead straight, direct, distant, dour, even, firm, fixed, flat, flinty, fundamentalist, grim, hard, hard-core, hidebound, horizontal, immovable, immutable, implacable, impliable, in a line, inductile, inelastic, inexorable, inextensible, inextensile, inextensional, inflexible, insociable, intractable, intractile, intransigent, iron, ironbound, ironclad, ironhanded, irreconcilable, irresilient, level, lineal, linear, loyal, muscle-bound, nonelastic, nonstretchable, obdurate, obstinate, offish, orthodox, procrustean, purist, puristic, puritan, puritanic, rectilineal, rectilinear, relentless, reserved, right, rigid, rigorist, rigoristic, rigorous, rock-ribbed, rockbound, ruler-straight, set, settled, single-minded, smooth, sot, standoffish, staunch, steadfast, steady, steely, stern, stiff, straight, straight-cut, straight-front, straight-side, straightlaced, straitlaced, streamlined, stubborn, TRUE, unaffected, unalterable, unapproachable, unbent, unbowed, unbroken, unchangeable, uncommunicative, uncompromising, uncurved, undeflectable, undeflected, undeviating, undistorted, unextendible, unextensible, unflappable, unflexible, ungiving, uninterrupted, unlimber, unmalleable, unmoved, unpliable, unpliant, unrelenting, unshaken, unswayable, unswerving, untractable, unturned, unyielding, upright, vertical, withdrawn