Who qualifies as an “ani” for maaser ani purposes

Nowadays, we can define as “poor” anyone who does not earn enough to cover normal living expenses, or is in debt with no way of covering it (i.e., he has no investments). Likewise, someone who usually gets by but is presently contending with irregular expenses that he can’t cover (e.g. medical expenses or marrying off his children), is considered to be poor and one can give him maaser ani.