Strewth is a slang term used primarily in Australia and New Zealand as an expression of surprise, shock, or disbelief. Though there isn't any exact synonym for it, there are other similar phrases that convey similar emotions, such as "crikey," "blimey," and "goodness gracious." These words are used primarily in the same context as strewth and are popular among English-speaking countries. Additionally, the phrase "holy cow" has a similar connotation and is sometimes used interchangeably. While strewth may be unique to Australian vernacular, these other phrases are used worldwide and can give a similarly colloquial and humorous tone to conversation.