The term 'strengthen' can be defined as making something stronger or more powerful. The crossword solutions for this term include 'BOOST' (5 letters), 'ENCOURAGE' (9 letters), 'BUTTRESS' (8 letters), 'PROP' (4 letters), 'BRACE' (5 letters), 'POWER' (5 letters), 'SINEW' (5 letters), 'STEEL' (5 letters), 'ANNEAL' (6 letters), 'beefup' (6 letters), 'ensteel' (7 letters), 'FORTIFY' (7 letters), 'NOURISH' (7 letters), 'shoreup' (7 letters), 'SUPPORT' (7 letters), 'TOUGHEN' (7 letters), 'REINFORCE' (9 letters), and 'intensiphi' (10 letters). All of these words are related to the idea of making something stronger, either through physical SUPPORT, emotional encouragement, or other means.