Damage Resistance
From FOnline: 2238 Wiki
Damage Resistance (DR) is a derived statistic in the SPECIAL character system that reduces damage done to a critter.
Any damage taken is reduced by this percentage, which means that if you wear an armor with 20 DR (Like the Leather Jacket) will reduce damage taken by 20%. Your Damage Resistance is, by then, only reduced by some perks or by armors.
Damage Resistance is a percentage, unlike the Damage Threshold (DT) that reduces a certain amount of damages before the Damage Resistance, that is at maximum 90%.
Note that armors feature a different Damage Resistance (And Damage Threshold) number for each type of damages taken (Normal, Electrical, Laser, Fire, etc.).