Dropping out of a respected educational institution/job/relationship and giving the reason "because I couldn't be bothered anymore", instead of being asked to leave (which would inevitably have happened a few weeks later).
This is a fairly common response to when performance falters and the person in question is aware that those responsible for the continuation of the current arrangement - be it work, education or a relationship - are close to severing ties.
The word is formed of two parts:
Toma/Tomme: a soft, french cow's milk cheese, created when there is too little milk to form a full cheese. (an analogy for the person's failure to complete their agreed contract)
Alone: a simple description of the feeling of isolation experienced by said person, once arrangement has been terminated. this can be through loss of contact with work/class mates, arguments with exes or simply a feeling of inferiority when comparing oneself to peers.
I think my mate is thinking about tommaloning, the principal has demanded a meeting next week, and he doesn't want to tell his parents he's been kicked out.