IPA: /ˈɡeɪmər/
KK: /ˈɡeɪmɚ/
A person who plays games, especially video or computer games, often regularly and with enthusiasm.
He is a dedicated gamer who spends hours playing online with friends.
Gamer → The word 'gamer' is derived from 'game' (from Old English *gamen*, meaning amusement or play) and the suffix '-er' (meaning a person who). A gamer is a person who engages in play or amusement, particularly in the context of video games or other games.
Think of someone who is a 'player' in a 'game' — the '-er' indicates a person, so a gamer is simply someone who plays games.