Penultimate is not a special pen... it means second last year of your degree (i.e. before you graduate!). Many companies often require applicants to be in your penultimate year.

What does penultimate year mean?

Well, penultimate means the one before the final one, you are correct by saying either penultimate or 2nd. Saying penultimate would probably be better though as it lets them know you are doing a 3 year course (as opposed to 4, 5 etc).

What is second penultimate?

But penultimate means “next to last” or “second to last.” It's probably because it adds an emphatic extra syllable to the word ultimate that people think it somehow means “more” than ultimate—but it really means less.