Everything he says is nonsense.
Don't listen to such drivel.
He was drunk and spouting one bit of nonsense after another.
Everyone just laughed it off as his nonsense.
でたらめ stresses that something is random or has no basis, while 戯言 stresses that the talk itself is foolish or worthless.
馬鹿話 is casual, often affectionate chatter about silly things, whereas 戯言 is a more literary, dismissive term for pointless or absurd speech.
たわごと is a blunt, often angry way to call something foolish nonsense, while 寝言 keeps a lighter, more mocking image of someone talking in their sleep.
寝言 literally means talking in one's sleep and is used figuratively for nonsense someone says while seemingly not thinking straight, while 戯言 refers to foolish talk in general without that sleep-related image.
Standard kanji spelling.
Kana spelling; common in casual writing.
Mixed kanji-kana spelling; less common but still used.
Out-dated kanji form; 戲 is the old form of 戯.
Irregular kanji usage; 譫 is not standard for this word.
The exact derivation is uncertain. The kanji 戯 (play, frolic) and 言 (word) combine to suggest playful or frivolous talk, which evolved into the meaning of nonsense.