a newborn calf; (metaphor) courageous and fearless young people who act with boldness, often appearing in the full expression 初生之犊不畏虎 chū​shēng​zhī​dú​bù​wèi​hǔ

to not be afraid of; to be undaunted

tiger; commonly referred to as 老虎 lǎo​hǔ