Which of the following is the definition for the underlined word?
At first, the woman's contractions were only intermittent, so the nurse had trouble determining how far her labor had progressed.

The word "intermittent" suggests that something occurs at imprecise intervals. "frequent" and "dependable" suggest the exact opposite of the meaning indicated in the sentence. "painful" likely reflects another element of the woman's labor, but it has nothing to do with the meaning of the word "intermittent".