Maisir

the agreement between participants is based on immoral inducement provided by entirely wishful hopes in the participants' minds that they will gain by mere chance, with no consideration for the possibility of loss.

Quranic verses (with translation) that at least discourage Maisir include:

Surah Al-Baqarah 219

Surah Al-Ma'idah 90

Surah Al-Ma'idah 91

Etymology

Both qimar and maisir refer to games of chance, but qimar is a kind—or subset—of maisir. Author Muhammad Ayub defines maisir as:

...wishing something valuable with ease and without paying an equivalent compensation for it or without working for it, or without undertaking any liability against it by way of a game of chance,

Another source—Faleel Jamaldeen—defines it as "the acquisition of wealth by chance (not by effort)". Ayub defines qimar as:

also mean[ing] receipt of money, benefit or usufruct at the cost of others, having entitlement to that money or benefit by resorting to chance;

Jamaldeen also refers to maisir as: "any game of chance".