A defense
parrying, stand, holding, withstanding, warding off, rebuff, obstruction, defiance, striking back, coping, check, halting, protecting, protection, safeguard, shield, screen, cover, fight, impeding, blocking, opposition, obstinacy; see also defense 1, objection 1, opposition 1.
Antonyms withdrawal*, acceptance, submission.
The power of remaining impervious to an influence
unsusceptibility, immunity, immovability, unalterableness, hardness, imperviousness, endurance, unyieldingness, fixedness, fastness, stability, stableness, permanence, invulnerability.
Antonyms vacillation*, susceptibility, variability.
The power of holding back another substance
retardation, nonconduction, friction, nonpromotion, attrition, reserve, surface resistance, detention, volume resistance, impedance.
An opposition
underground movement, partisans, maquis (French), insurgency, uprising, boycott, strike, walkout, slowdown, front, stand, guerrilla movement; see also revolution 2.