A semisolid thing is something that is not really a solid or a liquid. Mayonnaise is an example. Mayonnaise does not hold its shape like a solid but does not flow like a liquid. Normally semisolids are covalent things. Covalent substances get softer and softer until they melt. Ionic substances melt at one temperature and do not get softer. Butter can be a semisolid when it is warm. Butter does not hold its shape but it does not flow like a liquid.