"corrupt communication" - corrupt words. The error of much teaching/preaching simply because of whose feet the words land at.
Think carefully through the following verse, especially noting the words and their correct definitions. There is a very subtle parabolic message hidden to the natural mind.
"Let no corrupt communication proceed out of your mouth, but that which is good to the use of edifying, that it may minister grace unto the hearers." Ephesians 4:29