Step 1: Understand the given word.
MEEK means gentle, submissive, and quietly compliant; it describes someone who does not resist, complain, or assert themselves.
Step 2: Eliminate synonyms.
"Forbearing", "humble", and "mild" all share the quality of gentleness and patience, making them synonyms of meek rather than antonyms.
Step 3: Select the antonym.
"Impatient" means restless, intolerant, and not willing to endure calmly, which is the direct opposite of meek's submissive patience.
\[ \boxed{\text{impatient}} \]