What does to smear energy means in particle physics?

I’m reading about event selection for a particle physics experiment, english is not my first language, and there is this phrase I can not translate and understand: "The energy of the showers is found by smearing the summation of the ionizing depositions in argon. A smearing corresponding to a resolution of 15%$sqrt{E}$ is applied"

At first i thought the word "smearing" meant like gather or adding but then is used as a noun.

Thanks for the help!