Engineering has many definitions, which eventually come down to the art of intentionally manipulating behavior using specially crafted communication techniques.
For more information on social engineering, please refer to the following link: Watson, G. (2014). Social Engineering Penetration Testing. Elsevier. Paperback ISBN: 9780124201248. p.2
For example, SANS describes it as a euphemism for nontechnical or low-technology means such as lies, impersonation, tricks, bribes, blackmail, and threats used to attack information systems, and a social engineer is a hacker who uses brains instead of computer brawn. Hackers call data centers and pretend to be customers who have lost their password or show up at a site and simply wait for someone to hold a door open for them. Other forms of social engineering are not so obvious. Hackers have been known to create...