The term 'blocker' can be defined as something that prevents or hinders progress. In this crossword, the solutions are BETA (4 letters), SPAM (4 letters), DAN (3 letters), and IMPEDER (7 letters). BETA is a term used to describe a pre-release version of software that is made available for testing purposes. SPAM is an unsolicited email sent in bulk to multiple recipients. DAN is a Hebrew name meaning 'JUDGE'. IMPEDER is a verb meaning to hinder or impede. All of these terms relate to the concept of blocking or preventing progress in some way.