w=countermeasure&ls=a ] THESE [/url] say 'countermeasure' is either a solely plural word. It is a regular countable noun with '-s' plural. A couple of on-line dictionaries (Macmillan, the Free Dictionary) do list it only in its plural form ('countermeasures'), and it is indeed used that way more often, but not to the exclusion of the singular, I am sure.
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