There is an awfully large collection of confusing words you will encounter on first coming to study at Cambridge. You pick them up really quickly in the natural run of things, but I thought perhaps a mini-dictionary might be helpful. The list is alphabetised (if I’m competent enough, anyway) and may, like so many of my writings, grow. Apologies for my crude attempts at pronunciations for the non-obvious words, but it’s very hard to find someone who can read IPA.

• Boatie - one of the many people who row. Rowing is a very big thing at Cambridge, and some people are extremely dedicated to it (to the extent of getting up at six in the morning to train).
• Formal - a contraction of “formal hall”, this is an event in which you are served a three-course meal in college. Exceptions in the number of courses may apply between colleges, but I’m not aware of any non-three-coursers; exceptions also apply on special occasions, so the Jesus Christmas formal had seven courses (if I recall correctly). Usually you would wear a suit or mid-scale posh dress, with gown. Most formals start and end with a Latin grace. This is probably the closest experience to Hogwarts that Cambridge has to offer. You would almost always go to formal with other people you know (booking en-masse), as a celebration (such as for birthdays).
• Mathmo - a mathematician. The word is used to refer both to maths students, and also (less commonly) to people who may not be studying maths but who share the mildly Aspergers-y traits of stereotypical mathematicians. The word is very adaptable - so, for instance, a Trinity mathmo might be referred to as a Trinmo, a mathmo who enjoys applied courses rather than pure courses might be referred to as an appliedmo, and so forth. It can also (in some circles) be femininised as mathma.
• Muso - a music student.
• Natsci (pron. “nat-ski”) - a contraction of Natural Sciences, the subject studied by anyone who wishes to study a scientific subject. People studying (say) Biology would apply for Natsci, and then specialise later through judicious choice of courses. The Natscis are broadly subdivided into Physnatscis and Bionatscis. Also refers to Natsci students.
• Pennying - a drinking game (in the loosest sense of the word “game”, even for drinking games) fairly common across the UK, as far as I can tell. To my knowledge, the rules differ between Oxford, Durham and Cambridge; I present the Cambridge rules. If your drink is sitting on a surface, without your hand being contact with the glass, anyone else (though decorum dictates that this may only be done by people who are themselves drinking alcohol) is at liberty to drop a penny into the glass, whereupon you are honour-bound to down the drink. “An empty glass is a full glass” - that is, if an empty glass is pennied, you must fill your glass with drink and then down it. For this reason, it is wise to keep some liquid in your glass at all times. If you catch the penny in your teeth as you finish your drink, the pennier must down eir drink in turn. A “double penny” occurs when two people penny the same drink; in this situation, the second pennier must down eir drink, and the one who is pennied does not have to do so.
• Staircase - this is the generic term for where students live if they are in college - the very vertical equivalent of a block of flats. They are essentially the same as dormitories, and usually have their own kitchen(s). A house owned by the college and used as accommodation can be referred to as an external staircase.
• Swap - this is a sort of cross between a party and a speed-dating event. Usually they take the form of a formal (see above) or a trip to a local curry-house. They are designed to get lots of people who share an interest, or some sort of connection, to get to know each other very quickly. The Christ’s College hockey team might swap with the Jesus hockey team, for example, meaning that the teams go to a formal (or curry-house) and have a meal. Swaps are usually pretty ad-hoc; they are planned entirely by the people who are swapping.
• Tripos (pron. “try-poss”) - the Wikipedia article says it all, really, but this is the term used to refer to a course of study (the Mathematical Tripos, or the Historical Tripos, for example).