佶屈聱牙jí qū áo yá

字晦涩难解，不通顺畅达。

例佶屈聱牙的古书在青年实在不易理解，只徒糜费时日。——郭沫若《王阳明礼赞》

英difficult to pronunce or comprehend; be full of difficult and unpronounceable words;