Translation:The lie was serious.
I see that σοβαρό means also solemn. A serious lie can be considered as a lie that is said in a serious tone or as a lie that have serious consequences.
I'm not an English native speaker. Thank you for your answers.
The latter ;)
Σοβαρό is more like "severe". It even sounds and spells alike.
Good trick to remember the word. Thanks. ;-)