Final answer:
The term that best describes the actions of the unionized machinists at Larson Aeronautics is a 'strike', which is a halt in work initiated by employees to enforce demands.
Step-by-step explanation:
The actions of the unionized machinists at Larson Aeronautics, who have refused to work and halted production due to a breakdown in negotiations, is best described as a strike. A strike occurs when employees collectively stop working in order to gain concessions from their employer, such as higher wages, better working conditions, or other employment terms. Unlike a lockout, which is initiated by the employer, a strike is initiated by the employees or their union. Arbitration, mediation, and conciliation are methods used to resolve disputes and would typically be sought after a strike has begun to find a resolution between the conflicting parties.