The question "Have you ever been terminated or asked to resign from a job?" is a difficult one to answer on an application if the answer is "yes." However, your best bet is to take the "honesty is the best policy" approach. The question is specifically asking whether you have been fired from a job. Being asked to resign involuntarily is generally regarded is equivalent to being fired.
On the Application
In some cases, you won't see this question on a job application, though it may come up in the interview. Some applications simply ask it as a "yes or no" question. You may also see a follow-up asking you "why?" or if so, "please explain." Depending on the circumstance, you might provide a brief explanation or indicate something like, "Will gladly explain in an interview." Generally, you if the circumstances or complex, or you can't explain without coming across as overly critical of the employer, use the latter approach.
You may wonder why do you need to answer yes if the employer doesn't know? The simple answer is, they will check. Many employers do reference checks and background checks, and can easily verify whether you have been terminated. Reference checks with prior employers may reveal that you didn't leave on your own accord. A background check may uncover more details about your work history, and any gaps in employment. Employers typically have a zero-tolerance policy for deception in applications, resumes and interviews.
The Interview Setup
The reason to delay elaborating on your circumstances until the interview is that you can usually put your best foot forward at that point. On paper, a hiring manager only sees that you were terminated and their mind can wander into what you are like as an employee. If you have solid qualifications for the job, you may still get an interview. In the interview, indicating as concisely as possible why you were let go, what you have learned and accomplished since and what makes you a great fit for the current job can work well.
Cover Letter Approach
You can usually defuse the situation a bit before the interview with an effective cover letter. The primary purpose of a cover letter you submit with your application is to expound on things not present in your application or resume. In the letter, begin with specific points about your skills and experiences that relate directly with needs of the employer and position. After you have done so, you could tuck in a brief point that your application does note that you were terminated from a job. Ideally, this happened in the past. If so, you could indicate the same points about what you learned, and what you have done since the experience.