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) the damage taken will be reduced by 20%. Your Damage Resistance is, then, only improved by some perks, armors, and a few drugs.
Damage Resistance is a percentage, unlike the Damage Threshold (DT) which reduces a certain amount of damage before the Damage Resistance, that has a maximum of 90%.
Note that armors feature a different Damage Resistance (And Damage Threshold) number for each type of damage taken (Normal, Electrical, Laser, Fire, etc.).