Which of the following is most similar in meaning to the word 'smother'?

The word 'smother' means to extinguish a fire, stifle a person's breathing, or suppress a feeling or action. 'Suppress' is the closest synonym as it refers to the act of forcibly putting an end to something or keeping it from being revealed.

Step-by-step Derivation:
Step 1: Analyze the definition of 'smother'. In a literal sense, it means to kill by depriving of air; in a figurative sense, it means to stifle or overwhelm (e.g., smothering a flame or smothering an emotion).
Step 2: Evaluate Option A (Suppress). To suppress means to prevent the development, action, or expression of something. This aligns directly with the figurative meaning of smother.
Step 3: Evaluate Option B (Encourage). This is an antonym; to encourage is to stimulate or support, whereas smothering inhibits.
Step 4: Evaluate Option C (Instigate). To instigate is to bring about or initiate an action, which is the opposite of suppressing or smothering it.
Step 5: Evaluate Option D (Criticise). To criticise is to express disapproval; while one might criticise something they wish to smother, the act of criticism is not synonymous with the act of stifling.
Step 6: Conclusion: 'Suppress' is the only option that matches the semantic meaning of 'smother'.