Engineering and technology have a central role in shaping our reality that frequently goes unnoticed or not critically analyzed by engineers and engineering faculty and curricula. In so doing, the engineering that is taught, investigated (and improved), and practiced can unwittingly foster an ethical-political reality with which many engineers and engineering teachers may disagree. In this paper, drawing on literature from philosophy and sociology of technology and Latin-American liberating and decolonial traditions, the theoretical bases for a different engineering practice are set; an engineering committed to empowering people and constructing with them other possible socio-technical orders (and ethical-political realities). It can be called decolonial engineering. Then, grassroots (or popular) engineering, as it is practiced, taught, and improved (investigated) by some Brazilian university extension centres and groups, is presented and analyzed according to its decolonial foundations and outcomes. Finally, from grassroots engineering experience, some general traits of decolonial engineering education and research are derived.