No, hardwood flooring is not waterproof. Both engineered wood flooring and solid wood flooring can be water resistant to small amounts of water or liquid spillages, but they are in no way waterproof so any liquids should be wiped away from the surface of your flooring straight away.
If any amount of water (or other liquid) is left to soak into your flooring for a significant amount of time it can cause irreparable damage to your hardwood floor in the form of warping or distorting planks, and/or discolouration. This is why it is not recommended to install a hardwood floor in areas with lots of water, for example a kitchen, bathroom or utility room.
The best way to avoid water damage to your hardwood floor is by wiping away any accidents or liquid spills as soon as you notice them, remove outdoor footwear to ensure no water or debris is brought into your house, and place door mats at all entrance doors to wipe away any excess water from shoes or to place your wet outdoor footwear on. 
