Spray and Pray

Spray and Pray is a perk

Effects
Spray and Pray reduces the damage the Courier does to their companions by 75% (in other words, one only does a quarter of their normal damage to allies). It is primarily useful for rapid fire weapons used outside of V.A.T.S. (low critical hit chance weapons with a large area of effect, spread or high rate of fire) and Explosives skill weapons. However, in rarer cases, it can also be useful for high-damage single-shot weapons, such as sniper rifles. Sniper rounds can prove dangerous to a companion's longevity if hit, as it is will cost them a significant amount of health, and due to such weapon's critical hit multipliers, a shot in the back will likely become a sneak attack critical as well.

It is similarly effective at protecting companions from Meltdown and Heavy Handed automatic attack weapons such as the thermic lance and chainsaw, though on the latter two weapons it does not prevent them from being knocked around by Super Slam!

Behind the scenes
"Spraying and praying" is a term used to describe someone firing an automatic weapon at an opponent in long bursts with little to no regard for accuracy.