The answer is simple: The word gets used. When deciding what new words or phrases to include in an updated version of the dictionary (and how to define each), editors study language in use, including which words and phrases people use most often and how they use them.
Answer: A word gets into a dictionary when it is used by many people who all agree that it means the same thing. ... First, you drop the word into your conversation and writing, then others pick it up; the more its use spreads, the more likely it will be noticed by dictionary editors, or lexicographers.
Explanation words are added to dictionary so anytime you need you can use a dictionary to figure out the meaning of a word and how to pronounce it or spell it