undefensible

adjective

1. capable of being defended against assault or injury: The troops were bivouacked in a defensible position.
2. that can be defended in argument; justifiable.

adjective

1. capable of being defended, as in war, an argument, etc

adj.late 13c., from Old French defensable, from Late Latin defensibilem, from Latin defens-, past participle stem of defendere (see defend).