From page 56 of the manual:
Examining Creatures in Combat.
If the Character is in Combat Mode, a player who hovers the cursor over an enemy
creature will receive useful information in the Message Window. This
display will give an estimation of the Character’s likelihood of hitting the
creature with his primary weapon (see Figure 3-17). If some factor is reducing this
likelihood and the player can affect this factor, then an icon may appear to
indicate the presence of this reduction. Figure 3-18 shows all of the possible icons
which might appear in such a message. These icons, in order from left to right are:
the Weight (which tells us that a Character does not have sufficient Strength to
wield the weapon he holds), the Target (which indicates that one’s target is beyond
the range of one’s weapon), the Eye (which indicates that the target is beyond
Character’s range of Perception), the Wall (which informs us that the
target is hiding behind partial cover), the Bulb (which indicates that the target is
dimly illuminated), and the Red Cross (which informs us that the Character is suffering
an injury which affects his Combat Skills).