Yes, the PAL standard does have a vertical resolution and we can estimate the horizontal one. PAL is analogue but in most cases we can safely use the standard digital resolution 704×576 to represent a PAL picture. The details are below.
The vertical resolution is truly discrete
PAL is an analogue signal however it is defined to have 625 discrete lines in a frame because the lines are transferred and drawn discretely one by one. The visible part of the picture is defined to have 576 visible lines. The invisible part is needed for the beam in CRT to return back to the beginning to start drawing a new frame (the picture is drawn from the top left corner line by line).
The horizontal signal is fully analogue
As Hoppo wrote, in the horizontal direction there is no distinction of discrete pixels because this signal is analogue so the actual resolution depends on the bandwidth of the signal. For PAL the allowed bandwidth is defined to be 4.2 - 6 MHz (depending on the PAL variant). The whole line lasts 64 µs but the visible part is 51.9 µs. Again the rest is used for the beam in CRT to return from the right to the left. The bandwidth in the course of the duration of the visible part could allow up to about 622 "pixels" per line. Note also that the colour information has a lower bandwidth so its horizontal resolution is lower in analogue PAL.
For more information see PAL.
The corresponding digital resolution
There is also a corresponding digital resolution called 576i (or one variant of standard definition television) which is defined to have 576 lines with 704 (sometimes 720) pixels. The same frame frequency 25 Hz as in PAL is being used. See 576i and standard-definition television. In most cases it is safe to use this corresponding digital resolution 704×576 or 720×576 to represent a PAL picture.
The "i" means that the picture is displayed as interlaced. One frame (takes 1/25th of a second) is in fact displayed as two fields (50 per second). One field displays the even lines the second one the odd lines of the single frame. The full name of the resolution including the field rate is 576i50 or 576i/25 when referring to the frame rate.