For all you chemistry cats! in terms of covalent bonding, what is meant by an unshared (lone) pair of electrons?

It just means that those lone pairs can pair up with any other molecules according to the electronegativity, for example water ... H-O-H has two lone pairs on the O in order to satisfy the octet rule, each bond has two electrons as we can see H-O has to and O-H has another two + the two lone pairs (4) = 8