This is a very common word that can apply to a number of people who work in many different trades. The person who repairs your car may refer to themselves as an engineer, whereas someone who works in the manufacture of medicine may be called a chemical engineer. The word is almost always used to apply to someone who builds or repairs something.
Originally, however, the word came into popular use with the advent of trains and train travel, and it used to specifically refer to the person who ran the train. That era might be where the mispronunciation used most frequently came from; you may have heard it as "in-jee-near", but it's actually "en-gi-neer". The end of the word needs the closest attention, it's an "ee" sound as in "seen", as opposed to sounding like "near".