The term tipper can be used as a general term of reference for hitting with the tip of any attack, but is usually used in terms of the movesets of Marth and his clones and semi-clones, as well as the Home-Run Contest.
With Marth-based movesets
"Tipper" is typically used in reference to Marth's attacks and those of characters with movesets based on his. Marth's tippers are named so due to the end of his sword being the sweet spot and being stronger than the rest of his blade. Roy features a "reverse tipper", as his sweet spot is at the base of his blade while the rest of his sword is weaker. Lucina and Chrom, as a result of not having a particular sweet spot on their swords, have no hitbox distinction between tippers/reverse tippers and other hits, being deliberately designed as simpler, all-rounder versions of their parent fighter.
Generally, the term "tipper" can also be used to refer to the sweetspot of any attack, particularly those located at the tip, for example Ness's forward smash, which has a sweetspot on the tip of the bat. Several characters have tipper mechanics similar to Marth and Roy common across their movesets, although less accentuated. Most of Corrin's moves involving the Dragon Fang lance transformation have a tipper at the end of the spear, while moves involving the Omega Yato sword or other Dragon Fang transformations generally have no sweetspots and sourspots. Likewise, Byleth's Areadbhar has a tipper hitbox at the tip of the lance, with the shaft being significantly weaker, but other weapons carried by him have no such distinction. Shulk has a "reverse tipper" similar to Roy, with the blade of his Monado dealing slightly more damage than the energy beam. Simon and Richter have a tipper on the spiked ball of their Vampire Killer whip, with the chain being slightly weaker while the handle is significantly weaker. Sephiroth's Masamune combines aspects of both Marth and Roy's tipper: when used for thrusting, the tip of the blade is stronger, similarly to Marth, while if used for slashing, the center of the blade is stronger, similarly to Roy. Tippers are not exclusive to characters wielding swords or other melee weapons; for example, Mewtwo, Charizard and Ridley, all have a tipper hitbox at the end of their tails, and in the case of Ridley, of his wings.
In Home-Run Contest
Beginning in Melee, the Home-Run Bat's forward smash has several hitboxes that each do a varying amount of knockback, with the ones on the handle dealing the least and the ones at the tip dealing the most. As a result, hitting a tipper in the Home-Run Contest knocks Sandbag the farthest, and is the usual method of finishing Sandbag, unless the character has an attack that is stronger such as the Warlock Punch. The tipper still exists in normal play, though the distinction is typically irrelevant, as the non-tipper hitboxes are enough for a one-hit KO regardless.
An aerial tipper is a tipper in which one hits Sandbag while it is still in the air. In Melee, it sends Sandbag farther than a normal tipper due to the mechanics of the Sakurai angle; in Brawl and SSB4, this has been changed to a fixed angle, removing the distinction.