This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

adj. superlative form of happy: most happy.

"On the school's website, Mrs Wells says: 'As you may know, West Heath was the school at which Diana, later to become the Princess of Wales, spent what she described as the happiest days of her life."