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.

dev: ARAM Changes Incoming – League of Legends

Updates to ARAM

What is ARAM and why is it brilliant? Harnessing the chaos of

LoL Builds: Owning Noobs with Ashe in ARAM

ARAM God Title, Experience, and Thorough Guide : r/ARAM

We just set the world record with a 4 hour ARAM game : r

Simple League of Legends ARAM Guide

This LoL ARAM rune has been overpowered for 10 months and

dev: ARAM Changes Wrap-Up – League of Legends

Howling Abyss (League of Legends), League of Legends Wiki

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

dev: ARAM Changes Incoming – League of Legends

ARAM items tier list discussion : r/ARAM

This is how the start of every ARAM should look like : r

Let's ARAM it up – Zompist's E-Z rant page