정체가 · 정체를
traffic jam, congestion; stagnation
Example
퇴근 시간이라서 도로 정체가 심해요.
It's rush hour, so traffic is really backed up.
Word parts
정 stop+체 stagnate
Literally 'stopping and stagnating.' Homonym warning: 정체 also means 'true identity.'
Good to know
Common in traffic reports: 정체가 심하다 'heavy congestion'; in speech, 길이 막혀요 is more natural.