Thanks for your report. I'm not sure, but I presume you're referring to this:
(diretor de universidade)
It's not a bad translation: this sense of Eng. rector exists and is attested in the Concise Oxford Dictionary. The key issue for the lexicographer is that the roles, powers and terms of office of university heads may differ from case to case, making it difficult to give rock-solid equivalent translations. However, I've added the following: 'chancellor', which is the title in many universities in the UK, 'president' (US), plus 'head' for good measure. Please note that these changes won't be visible online for some time.