solidarize

[ sol-i-duh-rahyz ]
/ ˈsɒl ɪ dəˌraɪz /

verb (used without object), sol·i·da·rized, sol·i·da·riz·ing.

to unite or come together; become solidified.
Also especially British, sol·i·da·rise.

Origin of solidarize

From the French word solidariser, dating back to 1885–90. See solidary, -ize