In this English vocabulary question, choose the word that is opposite in meaning to 'Nebulous', an adjective that describes something vague, unclear or hazy.

Introduction / Context:
This vocabulary question checks your understanding of antonyms for descriptive adjectives. The key word is 'Nebulous', which is often used to criticise ideas, plans or explanations that are not clearly defined. In competitive exams you frequently encounter such words in reading comprehension and critical reasoning, so being able to match them with correct opposites is a valuable skill.

Given Data / Assumptions:
- Target adjective: 'Nebulous'.
- Options: 'Definite', 'Inchoate', 'Dismal', 'Sullen'.
- Exactly one option must express a clear opposite meaning.
- 'Nebulous' is taken to mean vague, unclear, ill-defined or hazy in this context.

Concept / Approach:
'Nebulous' literally recalls mist or clouds, and metaphorically refers to anything not clearly structured or sharply defined. Therefore its antonym should express clarity, precision and firm definition. In antonym questions, always identify the central contrast: here the contrast is between 'vague and hazy' versus 'clear and well-defined'. You then eliminate options that do not address this specific pair of ideas, even if they are positive or negative words.

Step-by-Step Solution:
Step 1: Understand 'Nebulous' as vague, indistinct or unclear, like a cloud. Step 2: Consider 'Definite'. This means clear, exact, with firm boundaries or certainty, which directly opposes vagueness. Step 3: Consider 'Inchoate'. This word is used for something just begun, incomplete or not fully formed, which is actually close to being vague and unclear. Step 4: Consider 'Dismal'. This describes something gloomy or depressing, which relates to mood, not clarity. Step 5: Consider 'Sullen'. This refers to a silently angry or gloomy attitude, again connected with temperament, not with how clear or unclear something is.

Verification / Alternative check:
If a plan is described as 'nebulous', you can rewrite the criticism as 'the plan is not definite'. The direct opposite would be to say 'the plan is definite and clear'. Substituting other options does not work: 'the plan is dismal' changes the meaning to 'sad or bad'; 'the plan is sullen' is incorrect usage; 'the plan is inchoate' still suggests vagueness and lack of development. Thus only 'Definite' successfully reverses the idea of 'Nebulous'.

Why Other Options Are Wrong:
'Inchoate' is wrong because it describes something underdeveloped or just starting, which often overlaps with being vague. 'Dismal' is wrong because it focuses on a gloomy or hopeless feeling, not on clarity. 'Sullen' is wrong because it describes a person's mood, particularly a sulky silence, not the sharpness or fuzziness of an idea. None of these contradict the key idea of being hazy or unclear, which is what 'Definite' does perfectly.

Common Pitfalls:
Students sometimes get attracted to rare words like 'Inchoate' and assume that if they do not know it well, it must be the correct answer. This is dangerous because many exam questions deliberately include rare synonyms or near-synonyms to mislead you. Instead, you should always rely on the core concept: 'Nebulous' equals vague and unclear, so its opposite must be a word you know that means clear and well-defined. 'Definite' is a straightforward, accurate and exam-friendly choice.

Final Answer:
The word opposite in meaning to 'Nebulous' is Definite.