The phrase 'split up' means to separate or divide into parts. There are various synonyms for this expression such as break up, disperse, disband, scatter, dissolve, part, sever, splinter, disintegrate, bifurcate, cleave, fracture, sunder, disjoin, detach, fragment, segregate, and divide. Each of these synonyms carries a slightly different nuance. For instance, 'disband' suggests ending a group or organization while 'scatter' implies a sudden and scattered dispersal. 'Fracture' indicates a broken and cracked separation. 'Cleave' and 'sever' denote a more forceful and permanent divide. By using these synonyms, we can add a more varied and diverse vocabulary to our communication.