Kadhaba

Kidhb, kadhib (الكذب) verbal nouns of kadhaba (كذب) which is often translated as "lying" is defined according to the Arabs as follows

هو الإخبار عن الشيء على خلاف ما هو عليه، عمدا كان أو سهوا

To give information regarding something which is opposed to what it really is whether done purposely or forgetfully.

Now you understand why the Companions (may Allaah be pleased with them) were so careful when narrating ahadiith and the Four Rightly Guided Caliphs did not narrate too many ahadith....