Scientists often use the phrase to describe organisms or pathogens that exhibit extraordinary resistance:
: Training in varied conditions—hot, cold, or even wearing non-traditional gear like hiking boots—to ensure the body can perform anywhere. 2. Biological Survival
: Using a "hybrid endurance" approach, such as combining running with rucking (walking with a weighted pack) to increase durability without the high impact of endless miles.
Metaphorically, the phrase applies to abstract concepts like hope or human spirit. For example, some argue that "though hope is frail, it's hard to kill," emphasizing that internal resolve often outlasts external hardship. It has also been used in business contexts, where "cockroach startups" are defined by their ability to survive lean times through extreme frugality and persistence.
: Low-maintenance options like the Snake Plant or ZZ Plant are often marketed as "hard to kill" because they thrive in low light and require minimal watering.
: The Washington Post notes that viruses like SARS-CoV-2 are "hard to kill" because they aren't technically alive; they are simply genetic material waiting for a host, making them resilient to many traditional environmental threats.
: For harsh climates, experts at Midwest Living recommend resilient species like Purple Coneflower , Salvia , and Lamb’s Ear , which are resistant to heat and drought. 4. Psychological and Existential Resilience