The tiger is one of the 12 Chinese zodiac animals and symbolizes bravery and power. The idiom 骑虎难下 (qí hǔ nán xià) means 'riding a tiger is hard to dismount' — stuck in a difficult situation.
usage
老 here is a prefix that doesn't mean 'old.' Chinese often adds 老 to animal names: 老鼠 (mouse), 老鹰 (eagle). 老虎 and 虎 both mean tiger.
