Keel over To suddenly collapse or fall over, usually due to exhaustion, illness, or a loss of balance. After running a marathon without proper training, he keeled over from exhaustion as soon as he crossed the finish line.

Black out To lose consciousness or memory temporarily, often due to a sudden shock, lack of oxygen, or excessive alcohol consumption. She drank too much at the party and ended up blacking out, unable to remember anything that happened after a certain point.

Pass out To lose consciousness suddenly and briefly, usually due to exhaustion, low blood pressure, or a medical condition. The heat was overwhelming, and the hiker started to feel dizzy before eventually passing out on the trail.

Topple over To fall over or collapse, often due to being unstable or unbalanced. The stack of books on the table was so high that it eventually toppled over, scattering books everywhere.

Give way To collapse or break under pressure, strain, or force. The old bridge gave way under the weight of the heavy truck, plunging it into the river below.

Cave in To collapse inward, often used in the context of roofs, ceilings, or structures. Due to the heavy rain, the weakened roof of the abandoned house finally caved in, causing extensive damage.

Conk out (1) To fall asleep quickly or suddenly, often due to exhaustion. After the party, I was so tired that I conked out as soon as I hit the bed.

Conk out (2) To suddenly stop working or functioning, often referring to mechanical or electronic devices. My computer conked out in the middle of an important presentation, leaving me scrambling to find an alternative way to display my slides.