Step 1: Understand the legal definition of intoxication.
Under the Indian Penal Code (Sections 85 and 86), intoxication refers to a state in which a person's mental faculties are impaired due to the consumption of alcohol or drugs, which may affect criminal liability.
Step 2: Eliminate incorrect options.
Emotional disturbance, physical disability, and old age are not recognised as intoxication under criminal law; they may constitute separate defences but not intoxication.
Step 3: Identify the correct definition.
Intoxication in criminal law specifically means a state of impaired mental condition caused by alcohol or drugs.
\[ \boxed{\text{A state of impaired mental condition due to alcohol or drugs}} \]