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

Quick Tips: Fundamental ARAM Strategy

ARAM Community Tier List - FINAL RESULTS (more details in post

Found a neat ARAM stats website (aramstats.lol) - you can even see

Aram tier list I've compiled after 18k~ arams : r/ARAM

Found a neat ARAM stats website (aramstats.lol) - you can even see

Special Game Modes in League of Legends

League of Legends Update Makes a Big Change to ARAM

What does ARAM stand for? : r/heroesofthestorm