Combine boiling water and bulgur in a bowl. Cover the bowl and let sit until water is absorbed, about 30 minutes.
Place chopped cucumber in a bowl and sprinkle with salt.
Whisk lemon juice, olive oil, garlic, lemon zest, and ground black pepper together in a bowl until dressing is well-combined.
Stir bulgur, chickpeas, cucumber, and green onions together in a bowl; pour dressing over bulgur mixture and toss to coat completely. Cover the bowl with plastic wrap and refrigerate until flavors combine, at least 1 hour.