A single jump overcall showing a good six-card suit and about 15-17 HCP or a seven-card suit and about 13-15 HCP.
Either hand would be suitable for a strong jump overcall of 3♣ if RHO opens one of some other suit.
Strong jump overcalls remain traditional at the rubber bridge table but have fallen into disfavour amongst tournament players, who generally prefer weak jump overcalls, which occur more often.