The article linked below is more than 20 years old but it is well worth reading.
http://www.lastdaysministries.org/na...ushouldgo.html
FROM THE ARTICLE:
What Is A Missionary?
A Christian missionary is a person whose passion is to make the Lord Jesus known to the whole world. They are completely under the command of King Jesus, and they will go anywhere, under any circumstances, for no pay, with poor living conditions and food, even though no one ever notices. They know that their Sovereign is watching every minute, and that is the only reward and joy they seek.
We see in the Bible that all Christians should continually be seeking every opportunity to lead the unsaved to Christ no matter where they are, for this is the privilege of every believer. But I believe that too many people use the word “missionary” too lightly - it's a term that has become misused in our everyday “Christian vocabulary.” Too many justify their not obeying the call of the Lord to go to the front lines of the battlefield, by saying they are “missionaries where they are.” I believe that “being a missionary” in the truest sense of the word is taking the Gospel
where it has never been before, or at least to a different culture or a different language group. A true missionary is someone who will risk
everything for the sake of the lost of this world.
Of course, as in every battle, not everyone can be on the front lines, for there are many things that are needed to aid those who are. But you must be clearly called by the Lord to stay away from those front lines before you can be assured that you are in the will of God. It is obviously true that many Christians are called to reach out to the lost in the ghettos, red light districts, and homosexual communities in their own areas. And there are always those faithful wives and mothers who diligently let Christ be known to their doctors, plumbers, and P.T.A. groups. These things bless God's heart, there's no doubt about it. Someone who loves Jesus should always be ministering His love no matter where they are. But every Christian should always be willing, ready, and “on-call” to leave everything at the command of their General, and go to a different “battlefield” to war against the king of darkness, bringing healing and light to “free the captives.”
The goal of a true missionary is to please and glorify their God by delivering the whole world into His hands and under His rule. It doesn't matter where they are stationed, for they are always at home in their Father's arms, no matter what the landscape or the language may be. They are only “aliens and strangers”
(I Peter2:11), and they are not concerned with trivial things like location or comfort. They are God's soldiers, perhaps hidden to our eyes, but always evident to His. Please, seek Him to see if you might be privileged to take the Gospel to those who have never heard it.