The phrase "laugh up" is a colloquial expression that can be used to describe a situation where an individual is laughing uncontrollably or excessively. There are several synonyms that can be used to replace the phrase "laugh up" such as "guffaw," "chuckle," "cackle," "snicker," "roar," and "howl." Each of these words conveys a slightly different tone or intensity of laughter, however, they all describe a lighthearted and happy moment. Whether it's a joke, a funny story, or a hilarious movie, there are plenty of reasons to laugh up and enjoy life's amusing moments.