The act of signing up, as for a commercial service.(noun)
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Use "signup" in a sentence
"Martin's Griffin: "Countdown" by Jonathan Maberry (Patient Zero) available in PDF download, but a signup is required."
"The logs services are not such a tragedy, one could use an application to monitor traffic (is not the same thing as server logs though) but the fact that they only accept refunds 5 days after signup is very bad."
"There isn't yet an affiliate program for recommending Google Apps, unless you count the Google Firefox or AdWords signup, which is kind of a stretch."