**Explanation:**

In parliamentary systems of government, various terms and procedures are used to conduct legislative business. These terms have specific meanings and are used to regulate the functioning of the parliament.

Let's analyze each option to determine the correct answer:

a) Countdown: This term is not directly related to parliamentary procedures or terms. It generally refers to the act of counting down to a specific event or deadline. Therefore, this option is not a parliamentary term.

b) Starred question: In parliamentary systems, questions are an important tool for lawmakers to seek information from the government. A starred question is a type of question that requires an oral answer from the concerned minister on the floor of the house. These questions are marked with a star to distinguish them from other types of questions. Thus, starred question is a parliamentary term.

c) Vote on account: A vote on account is a provision that allows the government to obtain parliamentary approval for a limited period of expenditure before the full budget is presented. It is a mechanism to ensure the continuity of government spending in the interim period. Therefore, vote on account is a parliamentary term.

d) Question hour: Question hour is a specific period during the parliamentary session where Members of Parliament can ask questions to ministers and hold them accountable for their actions. It is an important part of parliamentary democracy and allows for the scrutiny of government policies and actions. Thus, question hour is a parliamentary term.

Based on the above analysis, we can conclude that option 'A' (Countdown) is not a parliamentary term.