Terminology
There are three terms for this phenomenon. The most common by far is prestopped/prestopping. In descriptions of the languages of Southeast Asia, Australia, and the Pacific, preploded/preplosion is common, though prestopped is also used. In accounts of Celtic languages, preoccluded/preocclusion is used almost exclusively. Technically, nasals are already occlusives, and are often considered stops; however, some prefer to restrict the term 'stop' for consonants in which there is complete cessation of airflow, so 'prenasalized stop' and 'prestopped nasal' are not tautologies.
Read more about this topic: Prestopped Consonant