不通 has both physical and abstract meanings: 路不通 (road blocked), 电话打不通 (can't get through on the phone), 说不通 (doesn't make sense in speech/logic), 想不通 (can't figure it out / can't get over it).
usage
行不通 (xíng bù tōng) = won't work/infeasible. 此路不通 = dead end (literal sign on roads). 一窍不通 (yī qiào bù tōng) = completely ignorant (idiom: 'not a single aperture is open').
