adj

• Experiencing the effect of favourable fortune; favored by fortune or luck; fortunate, lucky, propitious.
  "How fares it with the happy dead?"
• (Of acts, speech, etc.) Appropriate, apt, felicitous.
  "happy coincidence"
• (in combination) Favoring or inclined to use.
  "slaphappy, trigger-happy"
• (rare, of people, often followed by "at" or "in") Dexterous, ready, skilful.
  "For inſtance, one lady can give an anſwer better than aſk a queſtion: one gentleman is happy at a reply; another excels in a rejoinder: one can revive a languiſhing converſation by a ſudden ſurpriſing ſentence; another is more dextrous in ſeconding; a third can fill the gap with laughing, or commending what has been ſaid."

noun

• (informal, rare) A happy event, thing, person, etc.
  "The strike split the Chicano community. Many workers at Farah crossed picket lines and continued to keep the plant operating. They were known as the "happies" because they wore buttons which featured a smiling face and the slogan, "I'm happy at Farah. …""

verb

• (intransitive, informal) Often followed by up: to become happy; to brighten up, to cheer up.
  "Whenever I started drinking again after abstaining for any period of time, it usually was an effort to relieve stress and to "happy up.""
• (transitive, informal) Often followed by up: to make happy; to brighten, to cheer, to enliven.
  "People really didn't want their Party Motivators in their photos, anonymous dancers, happying up the place. It spooked them."