The phrase "in a hundred" means the same thing as "one hundred." However, there are many synonyms for this phrase that can be used to add more variety to your writing or speech. Some examples include "a century," "a hundredfold," "a hundred times over," "a hundred percent," "to the tune of one hundred," and "a hundred in number." Additionally, expressions like "a ton," "a boatload," or "a plethora" can be used to convey a similar sense of abundance or magnitude. Synonyms like these can help to spice up your writing and make it more engaging for your audience.