Some definitions provided by the Wikipedia Glossary of Role-playing Game Terms. As of the current iteration of this guide, this is the most authoritative source available to me.
Adventure - “An adventure is a playable scenario in a tabletop role-playing game. These can be constructed by gamemasters[a] for their players, and are also released by game publishers as pre-made adventure modules. Different types of designs exist, including linear adventures, where players move between scenes in a predetermined order; non-linear adventures, where scenes can go in multiple directions”
Character sheet - “A character sheet is a record of a player character in a role-playing game, including whatever details, notes, game statistics, and background information a player would need during a play session. Character sheets can be found in use in both traditional and live-action role-playing games. Almost all role-playing games make use of character sheets in some fashion; even "rules-light" systems and freeform role-playing games record character details in some manner.”
Game master - “A gamemaster (GM; also known as game master, game manager, game moderator, referee, storyteller, or master of ceremonies) is a person who acts as a facilitator, organizer, officiant regarding rules, arbitrator, and moderator for a multiplayer role-playing gameThe act performed by a gamemaster is sometimes referred to as "gamemastering" or simply "GM-ing."
Player Character - “A player character (also known as a playable character or PC) is a fictional character in a video game or tabletop role-playing game whose actions are controlled by a player rather than the rules of the game…The player character functions as a fictional, alternate body for the player controlling the character”
Rules-Light - “A game system that uses very general mechanics, usually more focused on narrative actions in a game.”
TTRPG - An acronym for “Table-Top Role-playing games”