Iku 行 (go) and IU 言 (say) have the wrong definitions, they are reversed
These two basic kanji have their definitions swapped by accident
@Geoff - Actually the definition for 行くcorrectly says "to go". "to go" is also technically a correct definition for 言う (eg. "the cow goes moo"), but obviously that shouldn't be the main definition. Some definition priorities apparently got screwed up in the latest version of JmDict. I'll see what I can do there.
@Nicholas - "language" is one of the primary definitions of 言葉 in Jisho, ALC, Weblio, so I'm not sure what to tell you there.
I came to report this same problem since 言う came up on my practice but it still says to go. Also the word 言葉 (ことば) has the definition "language" but it simply means "word", 言語 means language.