You are under no obligation to answer questions from your doctor about your smoking habits. If asked, simply decline politely to answer the question.
According to Health Markets (https://www.healthmarkets.com/content/what-you-need-know-about-smoking-and-health-insurance), "Tobacco use is defined as 'any tobacco product, including cigarettes, cigars, chewing tobacco, snuff, and pipe tobacco, used four or more times a week within the past 6 months.'” So, if you are an infrequent pipe smoker, you can truthfully answer "no."
When it comes to life insurance, failure to admit to using tobacco can result in being denied coverage and lying can result in your insurance being cancelled or a life insurance claim being rejected.
However, if you are a pipe smoker, you should tell your dentist so that he can check for oral cancer during check ups.