* "He claimed to be helping me, but I suspected he had ulterior motives." (meaning he had hidden or secret reasons)
* "The politician's seemingly generous donation had an ulterior purpose: to gain votes." (meaning the purpose was not what it seemed)
* "Don't let her sweet smile fool you, she has an ulterior agenda." (meaning she has a hidden plan)
The word "ulterior" is always used with the word "motive" or "purpose" to suggest that there is a hidden or secret reason for something.