Ghosting is an online term that can have at least two meanings
Ghosting can mean the viewing of a stream
for the purpose of gaining information that could be used to gain an advantage against them (no matter if they're a team or an individual)
Ghosting can mean the shutdown/ceasing of communication with someone without notice. This can include but doesn't always require the closing or shutting down of social media accounts or ports of contact such as email addresses or phone numbers.
First Example - In an esports
tournament watching a stream of the game you/your team are playing for to gain an unfair advantage over the enemy. Thus you have ghosted the enemy.
Second Example - When you do not wish to continue a friendship or relationship with someone you might decide to cease all communication with them. Ghosting them.