lack. not to have or not to have enough of it What we lack in this house is space to store things .I lack the energy that is required to look after the bab The reception seems to be lacking in warmth a diet lacking in nutritional value will not keep a person health . I dare not take part in the speech contest for lack(n )of couragelack: not to have or not to have enough of it  What we lack in this house is space to store things.  I lack the energy that is required to look after the baby.  The reception seems to be lacking in warmth.  A diet lacking in nutritional value will not keep a person healthy.  I dare not take part in the speech contest for lack (n.) of courage