Two questions for you:

1)    What is the meaning of dhikr?

2)    Is it permissible to make dhikr wherever you want?

In the Name of Allah, the Beneficent, the Merciful,

All praise is due to Allah, and may peace and blessing be upon the Messenger of Allah, upon his household, his companions and those who have followed him. To proceed:

Dhikr is to remember Allah (Mighty & Majestic) by His Most Beautiful Names and Attributes, whether that is by praising Allah (Glorious & Exalted) with these Names and Attributes, by teaching this to His bondservants and urging them to do so, by remembering Allah and thinking about His blessings and favors or remembering Him through His commands and prohibitions, whether that is by carrying out His commands and following His prohibitions or by teaching them to others. It is permissible for you to remember Allah with your tongue wherever you please, except in places like bathrooms where people relieve themselves.

As for remembering Allah with your heart, this is permissible in any and every location, for the dhikr of the heart is prescribed in every time and place: in the bathroom and otherwise.

What is disliked in the bathroom and other places of the sort is to remember Allah with the tongue. That is out of reverence for His Grandeur, Exalted as He is above all imperfection. The only exception is to say, “Bismillah,” upon performing ablution. If it would not be feasible to perform ablution outside the bathroom, one should say it, because it is obligatory according to some of the People of Knowledge and it is a confirmed Sunnah according to the majority of scholars.

And Allah Almighty is the Most High, and He knows best.