Someone is holding a Poké Ball of any type. (it may be a Master Ball, a Repeat Ball, etc.)
This often happens — both in licensed works and in fan art — when Pokémon Trainers, with fighting stance-like poses, are ready to call out a member of their team for a battle.
The following tags are aliased to this tag: holding_pokeball.
This tag implicates holding, poke_ball.
Read the full article.