Related Clues:

• Like gastric juice
• Cause of much bellyaching?
• Vitriol
• Rain contaminator
• Dropped drug
• Low-pH
• Kind of comment
• Etching aid
• Litmus-paper reactant
• Vicious
• Rudely sarcastic
• Battery contents
• With 44-Across, polluted precipitation
• Word with rock, rain or test
• Caustic liquid