Haki is a type of power used in the manga or anime, One Piece.
Haki is divided into 3 types, Observation/Kenbunshoku Haki, Armament/Busoshoku Haki and the most difficult and rare, Conquerors/Haushoku Haki.

1. Observation Haki
Kenbunshoku Haki is a form of Haki that grants the user a sixth sense that allows them to sense the presence, strength, and emotions of others, as well as gain limited precognitive abilities. In Skypiea, it is named Mantra.

2. Armament Haki
Busoshoku Haki is a form of Haki that allows the user to use their own spiritual energy to create, in essence, an invisible armor around themself, providing incredible offensive and defensive capabilities. this form of Haki can be used to injure Devil Fruit users that are otherwise immune to ordinary physical attacks, such as Logia users. eg. Luffy's Elephant Gun.

3. Conquerors Haki
Haoshoku Haki is a rare form of Haki that allows the user to exert their own willpower over others. This type of Haki cannot be attained through training; it is a power that one must be born with. Only one in several million people are born with this ability. Haoshoku Haki is considered an extremely dangerous threat and a highly valuable asset by powerful groups such as the Marine Admirals and the Four Emperors.

A term used to reference cannabis/marijuana/weed.

A awesome cool incredible sweet person who is tough, but makes a good friend

You call someone Haki when he/she is a really cheap person. Even though they have more than enough money, they always want to get the cheapest stuff or rip people off so that they don't spend their money.

An addictive substance to girls with low self esteem

Haki is a word to describe someone who has subtle underlying confidence and aspires to make themselves and others feel good.