vulnerable — capable of or susceptible to being wounded or hurt, as by a weapon: a vulnerable part of the body.
unimaginable — capable of being imagined or conceived.
unthinkable — inconceivable; unimaginable: the unthinkable size of the universe.
certain — If you are certain about something, you firmly believe it is true and have no doubt about it. If you are not certain about something, you do not have definite knowledge about it.
untenable — incapable of being defended, as an argument, thesis, etc.; indefensible.
improbable — not probable; unlikely to be true or to happen: Rain is improbable tonight.
irrational — without the faculty of reason; deprived of reason.
unbelievable — too dubious or improbable to be believed: an unbelievable excuse.
unlikely — not likely to be or occur; improbable; marked by doubt.
unreasonable — not reasonable or rational; acting at variance with or contrary to reason; not guided by reason or sound judgment; irrational: an unreasonable person.
indefensible — not justifiable; inexcusable: indefensible behavior.
unjustifiable — capable of being justified; that can be shown to be or can be defended as being just, right, or warranted; defensible: justifiable homicide.
vindicable — capable of being vindicated: a vindicable expedient.
