If something is broken or lost but can be put back together, or replaced, then it is reparable. You may be disappointed if someone knocks over your house of cards, but you can take comfort knowing that the structure is reparable.
Reparable is a close relative of its more common synonym repairable (both basically mean “able to be repaired"). The word reparable, though, is usually reserved for damages or injuries that can be reversed or losses that can be replaced, while the word repairable is more for things or problems that can be fixed. For example, if your friend broke your glasses, they are repairable, but if he hurt your pride, it is reparable — hopefully.