I think it usually is a bit more specific than this. Typically the
entry refers to the angle or half angle (assuming symmetry along the
center line) of the water plane a the bow. A fine entry or small half
angle can be achieved by having a narrow water-plane that comes to a
point or by having hollows near the bow. Narrow boats can have full
entries (if you cap a PVC pipe and throw it in the water it has a high
Length/Beam ratio but a bluff bow) and wide boats can have fine entries
say a Buzzards Bay 12 1/2...

-- Tom.