To solve the given question, we need to identify which compound among the options is known as Carbolic acid. Let's evaluate each option:

1. Phenol: Phenol is a type of aromatic compound with the chemical formula C_6H_5OH. It is commonly referred to as Carbolic acid. Historically, it was used as an antiseptic and disinfectant.
2. Alcohol: Alcohol refers to a group of organic compounds characterized by one or more hydroxyl groups (-OH) linked to a carbon atom. Examples include ethanol and methanol. Alcohol is not known as Carbolic acid.
3. Ether: Ether is a class of compounds with an oxygen atom connected to two alkyl or aryl groups (R-O-R'). Common examples include diethyl ether. Ether is not known as Carbolic acid.
4. Acetone: Acetone, with the formula C_3H_6O, is a simple ketone used primarily as a solvent. Acetone is not known as Carbolic acid.

From the explanations above, it is evident that phenol is the compound referred to as Carbolic acid. Therefore, the correct answer is:

Phenol

Phenol is known as Carbolic acid due to its historical use in carbolic treatments and antiseptics. It plays a significant role in the production of various industrial and cosmetic products, acting as an intermediate in the manufacture of plastics and other chemicals.