The term '1827' is used to refer to the pairing of Hibari and Tsuna in Katekyo Hitman Reborn!. It is probably the hottest pairing aside from 6927, which is Mukuro and Tsuna.

A pubic hair piece. A toupee for the pubic area/genitals. In the 1700’s when mercury was used to treat sexually transmitted diseases (Gonorrhea or Syphilis) one of the side effects was the loss of pubic hair. To disguise this condition, that was not cured by mercury, a Merkin was employed.

Refers to the yaoi pairing between Hibari Kyoya (note, this is last name first, first name last basis. Japanese names.) and Tsunayoshi Sawada in the Katekyo Hitman Reborn! fandom. Fangirls use 18 to refer to Hibari and 27 to refer to Tsuna.

Although this pairing is one of most popular pairings in the fandom, it is not canonical-not as much as, persay, 6918 (Mukuro X Hibari), D18 (Dino X Hibari), 5927 (Gokudera X Tsuna) or R27 (Reborn X Tsuna). {8059 is one of the most popular AND canonical pairings in the fandom...but this is about Hibari and Tsuna here. Not Yamamoto and Gokudera}.

With this pairing (and almost every other Tsuna-centric pairing in the Reborn! fandom), Tsuna can almost always be found as the uke (bottom). Because of that, it is suggested that Tsuna should never top Hibari, lest the fangirl mob lynch the offender.

When writing 1827, fanfiction authors tend to make Hibari as OOC as possible, while Tsuna becomes an attention whore. Contrary to the definition above, both 1827 and 6927 are not hot, since 6927 involves raep-even though if viewed in some lights, it can be found more canonical than 1827...while 1827 is just a smashing of the two most popular characters in Reborn!.