ARAM - What does ARAM mean in LoL?

ARAM stands for "All random all mid." See an example of how people use it.
League of Legends (LoL) players use ARAM to refer to the All Random All Mid game mode. In this mode, players are assigned random champions (from their pool of owned champions) and forced to fight in a single lane.

Simple League of Legends ARAM Guide

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How a Challenger plays ARAM in League of Legends

Ultimate LOL Aram Guide: Best Tips For You to Win - Eloking

Ultimate LOL Aram Guide: Best Tips For You to Win - Eloking

ARAM 2023: Preview - League of Legends

Does anyone know how the ARAM matchmaking works? I know it doesn't

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ARAM items tier list discussion : r/ARAM