The nearest point a star reaches in its circuit around the centre of a galaxy. One of the two apsides of its motion. The other, the opposite point, is its apogalacticon.
The perigalacticon of our Sun is about 27 600 light years, and is about 7% closer in than the apogalacticon (the orbital eccentricity is 0.07). We are currently near this, at 27 700 light years from galactic centre, and will reach it in 15 million years, which is less than one twelfth of the Sun's period of revolution about the galactic nucleus (the galactic year).
The Sun does not simply revolve in the galactic plane. It crossed the plane 2 million years ago and is now 50 light years above it. At perigalacticon we will be 250 light years above it, which is coincidentally the highest elevation we attain. (The period of this vertical oscillation is 32 million years or about 3.5 times per galactic year.)
Halo stars, a rare kind of star, have much greater eccentricities than this, with a very large difference between perigalacticon and apogalacticon.
Source and reading. I found this web page informative:
http://www.ottawa.rasc.ca/observers/an9701p3.html