a crop-devouring locust, named for finishing a field off and leaving nothing behind
The name is an accusation rather than a species label. Hebrew built it from a verb meaning "to consume, finish off, strip bare" (חָסַל), so the word says something close to "the finisher" or "the stripper." It tells you what the insect did to a harvest, not how big it was or what it looked like, exactly the way another locust name in the same list means roughly "the shearer" (גָּזָם).
Outside Joel the word never travels alone. It stands beside the ordinary Hebrew word for locust (אַרְבֶּה) in Solomon's list of national disasters worth praying about, and again in the psalm that retells the plagues on Egypt, where God hands one nation's crops to this creature and the fruit of their labor to the other. The pairing is not a distinction between two bugs; it is a way of saying "locusts of every kind, and nothing left."
In Joel the word closes a chain of four locust names, each wave eating whatever the wave before it left, so this one arrives last and finishes the job. When the same four names come back in the promise of restoration, they come back in a different order. That reshuffling is the main reason most scholars no longer read the four as four species, or as four stages in one insect's growth: a prophet describing a life cycle would not rearrange the stages. The four names are better heard as four angles on one catastrophe, one insect accused of cutting, of swarming, of licking the ground bare (יֶלֶק), and of finishing off.
One verse turns the picture outward. In Isaiah 33:4 no crop is in view at all: a defeated army's plunder is swept up the way this locust sweeps a field, and the swarm that normally pictures the invader now pictures those who strip the fallen invader clean.