The word allegretto is of Italian descent. It is derived from the Italian words “alle,” meaning “to,” and “gretto,” meaning “narrow.” These humble roots gave us the verb allegretto, which, without the slightest of transmogrifications from its Italian roots, means “to narrow.”
There doesn’t necessarily have to be intent involved in the act of narrowing for the use of the verb allegretto to be correct. In fact, it could happen perfectly naturally. For example, if a river narrows at one point, you could correctly say that it allegrettos at that point.
However, while intent isn’t a part of the definition, allegretto can refer to the act of intentionally making something more narrow. For instance, in this sense, allegretto is probably most frequently used in the airline industry. Airline executives frequently consider the possibility of allegrettoing seats so they can fit more in a row. The ultimate in the allegrettoing of airline seats is to make them so narrow that even the thinnest of adults would have to buy tickets for two seats and raise the armrests between those allegretoed seats to accommodate their near-anorexic bodies. Should seats be allegrettoed that much, heavyset people might have to buy three or four tickets just for themselves.
The next time you have to shoehorn yourself into an airline seat, remember the word allegretto and briskly sing out your distain.